Output stage of digital-to-analog converter

Abstract

The invention relates to an output stage of a digital-to-analog converter. An example apparatus includes: a first transconductance amplifier (202); an amplifier (204), a first input of the amplifier (204) coupled to a first output of the first transconductance amplifier (202), a second input of the amplifier (204) coupled to a second output of the first transconductance amplifier (202); a resistor (206), a first terminal of the resistor (206) coupled to an output of the amplifier (204); and a second transconductance amplifier (208), a first input of the second transconductance amplifier (208) coupled to a second terminal of the resistor (206), a second input of the second transconductance amplifier (208) coupled to an output of the amplifier (204) and a first terminal of the resistor (206), a first output of the second transconductance amplifier (208) coupled to a first output of the first transconductance amplifier (202) and a first input of the amplifier (204), a second output of the second transconductance amplifier (208) is coupled to a second output of the first transconductance amplifier (202) and a second input of the amplifier (204).

Description

Technical Field

[0001] This specification generally relates to amplifiers, and more specifically, to the output stage of digital-to-analog converters. Background Technology

[0002] In electrical systems, control circuits such as controllers, processors, and state machines can generate digital control signals. Such electrical systems can include industrial automation systems, irrigation systems, automotive systems, building automation systems, etc. These systems include digital-to-analog converters (DACs) for converting digital signals to analog signals, and output stages for providing analog voltages or currents based on the generated analog signals. The analog current or voltage is transmitted to one or more devices, such as peripheral devices, field devices, sensors, valves, actuators, etc. One or more devices perform one or more actions or operations based on the analog current or voltage. Summary of the Invention

[0003] For the output stage of a digital-to-analog converter, an example device includes a first transconductance amplifier having a first output and a second output. The device also includes an amplifier having a first input, a second input, and an output, the first input of which is coupled to the first output of the first transconductance amplifier, and the second input of which is coupled to the second output of the first transconductance amplifier. The device further includes a resistor having a first terminal and a second terminal, the first terminal of which is coupled to the output of the amplifier. The device also includes a second transconductance amplifier having a first input, a second input, a first output, and a second output, the first input of which is coupled to the second terminal of the resistor, the second input of which is coupled to the output of the amplifier and the first terminal of the resistor, the first output of which is coupled to the first output of the first transconductance amplifier and the first input of the amplifier, and the second output of which is coupled to the second output of the first transconductance amplifier and the second input of the amplifier. Other examples are described.

[0004] For the output stage of a digital-to-analog converter, one example device includes a positive voltage power supply terminal. The device also includes a negative voltage power supply terminal. The device further includes a first transconductance amplifier having a first output and a second output. The device also includes an amplifier having a first input, a second input, and an output, the first input of which is coupled to the first output of the first transconductance amplifier, and the second input of which is coupled to the second output of the first transconductance amplifier. The device further includes a resistor having a first terminal and a second terminal, the first terminal of which is coupled to the output of the amplifier. The device also includes a second transconductance amplifier having a first input, a second input, a first output, and a second output, the first input of which is coupled to the second terminal of the resistor and the positive voltage power supply terminal, the second input of which is coupled to the negative voltage power supply terminal, the first output of which is coupled to the first output of the first transconductance amplifier and the first input of the amplifier, and the second output of which is coupled to the second output of the first transconductance amplifier and the second input of the amplifier. Other examples are described.

[0005] For the output stage of a digital-to-analog converter, an example device includes a first switch having a first terminal and a second terminal. The device also includes a second switch having a first terminal and a second terminal. The device further includes a third switch having a first terminal and a second terminal. The device also includes a fourth switch having a first terminal and a second terminal. The device further includes a fifth switch having a first terminal and a second terminal, the second terminal of which is coupled to a common terminal. The device also includes a first transconductance amplifier having a first output and a second output, the first output of which is coupled to the second terminal of the second switch and the second terminal of the third switch, and the second output of which is coupled to the second terminal of the first switch and the second terminal of the fourth switch. The device further includes an amplifier having a first input, a second input, and an output, the first input of which is coupled to the first output of the first transconductance amplifier, the second terminal of the second switch, and the second terminal of the third switch, and the second input of which is coupled to the second output of the first transconductance amplifier, the second terminal of the first switch, and the second terminal of the fourth switch. The device also includes a resistor having a first terminal and a second terminal, the first terminal of which is coupled to the output of the amplifier. The device further includes a second transconductance amplifier having a first input, a second input, a first output, and a second output. The first input of the second transconductance amplifier is coupled to a second terminal of the resistor. The second input of the second transconductance amplifier is coupled to the output of the amplifier and the first terminal of the resistor. The first output of the second transconductance amplifier is coupled to a first terminal of a first switch. The second output of the second transconductance amplifier is coupled to a first terminal of a second switch. The device also includes a third transconductance amplifier having a first input, a second input, a first output, and a second output. The first input of the third transconductance amplifier is coupled to a second terminal of the resistor and the first input of the second transconductance amplifier. The second input of the third transconductance amplifier is coupled to a first terminal of a fifth switch. The first output of the third transconductance amplifier is coupled to a first terminal of a fourth switch. The second output of the third transconductance amplifier is coupled to a first terminal of the third switch. Other examples are described. Attached Figure Description

[0006] Figure 1 This is an example system that incorporates the instances described herein, and includes programmable logic controllers for transmitting control signals to field devices.

[0007] Figure 2 yes Figure 1 A circuit diagram of an example implementation of the output stage.

[0008] Figure 3 yes Figure 1 Circuit diagram of an alternative example implementation of the output stage.

[0009] Figure 4 yes Figure 1 Circuit diagram of an alternative example implementation of the output stage.

[0010] Figure 5 yes Figure 1 A circuit diagram of an example implementation of the output stage.

[0011] Figure 6 yes Figures 2 to 5 Circuit diagram of an alternative example implementation of a transconductance amplifier.

[0012] Figure 7 This is a graph showing the common-mode suppression ratio corresponding to the examples described in this article.

[0013] Use the same reference numerals or other reference indicators in the drawings to indicate (functionally or structurally) the same or similar features. Detailed Implementation

[0014] The drawings are not necessarily drawn to scale. Generally, the same reference numerals in the drawings and this specification refer to the same or similar parts. Although the drawings show areas with clear lines and boundaries, some or all of these lines or boundaries may be idealized. In reality, boundaries or lines may be invisible, mixed, or irregular.

[0015] Electrical systems such as industrial automation systems, irrigation systems, automotive systems, and building automation systems utilize digital-to-analog converters (DACs) to convert digital control signals from processors or controllers into analog voltage or current signals. These analog voltage or current signals are then transmitted to devices to control them. For example, a controller can provide control signals to devices such as temperature sensors, valves, actuators, or other computing devices. The devices then perform one or more actions or operations based on the control signals. The DAC may be included in or coupled to an output stage for converting analog signals into higher-power analog voltages or currents.

[0016] The output stage utilizes one or more feedback loops and a forced amplifier to apply the DAC signal to the output terminal. The feedback loops provide closed-loop feedback to the forced amplifier to apply the DAC signal to the output terminal. The output stage can be a current output stage, a voltage output stage, or a current / voltage output stage. A current output stage is an output stage that provides an analog current signal to the device based on the analog DAC output signal. A voltage output stage is an output stage that provides an analog voltage to the device based on the analog DAC output signal, and a current / voltage output stage is an output stage structured to output an analog current signal or an analog voltage signal to the device based on the analog DAC output signal.

[0017] Some output stages utilize instrumentation amplifiers (INAs), such as voltage feedback amplifiers, in the feedback loop. Such INAs output voltage based on the voltage difference between the inputs. For a current output stage, the input corresponds to the current supplied by the output stage. For a voltage output stage, the input corresponds to the output of the voltage output stage and the negative voltage source (VSN) terminal connected to the ground terminal of the field device. Voltage feedback INAs are used because they have limited noise and provide linearity. However, the INA uses resistors to transform the common-mode signal present at the input terminals into a signal that allows the amplifier to operate. As used herein, common-mode refers to the difference between the device's local ground and the actual factory or earth ground. For example, the output stage of a DAC is referenced to a first local ground, and the input stage of the field device is referenced to a second local ground. The first and second local grounds may differ from the factory or earth ground. Therefore, the common-mode voltage of the transmitting device utilizing the DAC may differ from the common-mode voltage of the receiving device (e.g., the field device).

[0018] The INA utilizes local ground to provide feedback. However, the INA output is based on the common-mode difference between the transmitting and receiving devices. Furthermore, the transmitting device is unaware of the receiving device's local ground. Due to the common-mode difference between the transmitting and receiving devices, the resistors implemented in the INA come into play, modulating the common-mode resistance and thus producing a common-mode rejection ratio (CMRR). CMRR indicates the ability to suppress the common signal between the two inputs of the INA. The higher the CMRR, the better the INA suppresses the common signal. Ideally, the amplifier senses the difference between the two signals, unaffected by the receiver's common-mode. However, because the signal received by the INA is referenced to the receiver's local ground and includes at least one resistor coupled to the transmitter's local ground, the INA is affected by the receiver's common-mode when transmitting the difference between the two signals.

[0019] As described above, resistors in an INA help improve CMRR. However, the amount of CMRR is limited by the characteristics of the resistors. For example, the greater the resistance variation between resistors, the lower the CMRR of the INA. To produce accurate results, the resistors in an INA need to be identical, which may be difficult or even impossible to achieve without expensive, large resistors. Therefore, the accuracy of the system is limited by any sensitivity to common-mode error. For example, using a DAC with an accuracy up to 0.002% of full scale, the full-scale accuracy of the system may be limited to 0.1%. To improve CMRR to above 80 dB, thereby improving the accuracy of the system, such an INA-based feedback output stage would require very large resistors or an expensive, complex, and extensive trimming process.

[0020] The examples described herein include an output stage that utilizes a current feedback amplifier, such as a transconductance amplifier, to improve the common-mode rejection ratio (CMRR) to above 120 dB without trimming or large resistors. The described current feedback amplifier has better common-mode rejection because it is not referenced to local ground, thus reducing sensitivity to common-mode differences between the transmitting and receiving devices. Although some current amplifiers have worse linearity and higher noise than voltage amplifiers, the current amplifier described herein incorporates circuitry for voltage amplification, which improves both noise and linearity. Therefore, the examples described herein enable an output stage with a CMRR above 120 dB without the need for trimming or large resistors. Furthermore, the examples described herein allow for higher loop bandwidth and slew rate, as well as current output impedance exceeding 450 megohms, without the need for trimming. Thus, the examples described herein enable DAC output stages with lower cost, smaller footprint, high performance across temperature and lifespan, and high-speed operation.

[0021] Figure 1 An example electrical system 100 is shown. Figure 1 The electrical system 100 includes an example programmable logic controller 101, which includes an example processing unit 102, an example DAC 104, an example output stage 106, a positive voltage supply (VSP) terminal 108, and a negative voltage supply (VSN) terminal 110. The electrical system 100 further includes an example field device 112, which includes an input stage 114. Furthermore, one or more components of the programmable logic controller 101 or the field device 112 may be removed or combined. Additionally, extra components may be added to the programmable logic controller 101 or the field device 112.

[0022] Figure 1The programmable logic controller 101 can be a central processing unit that controls one or more field devices, including field devices 112. For example, the programmable logic controller 101 can provide analog voltage or current to the field devices 112, and the field devices 112 can perform actions or operations based on the analog voltage or current.

[0023] Figure 1 The processing unit 102 generates digital signals, which are converted into analog signals to control the field device 112. The processing unit 102 includes two outputs (also referred to as output terminals). A first output of the processing unit 102 is coupled to a DAC 104. A second output of the processing unit 102 is coupled to an output stage 106. The processing unit 102 generates one or more control signals to control the field device 112. The one or more control signals are digital control signals corresponding to one or more digital values ​​that correspond to actions or operations. The processing unit 102 provides the digital control signals to the DAC 104. Furthermore, based on the characteristics of the field device 112, the processing unit 102 may provide an offset value to the output stage 106. For example, the DAC 104 may be structured to output an analog signal between 0 volts (V) and 10 V, and the receiver operates between -5 V and 5 V; the processing unit 102 can provide an offset value to ensure that the output stage 106 provides a signal between -5 V and 5 V to the receiver, even if the DAC operates between 0 and 10 V. The processing unit 102 may be a processor, controller, graphics processing unit, central processing unit or any other processing unit.

[0024] Figure 1 The DAC 104 converts the digital signal from the processing unit 102 into an analog signal. The DAC 104 includes an input (also called an input terminal) and an output. The input of the DAC 104 is coupled to the processing unit 102, and the output of the DAC 104 is coupled to the output stage 106.

[0025] Figure 1Output stage 106 can be a force-sense system, a Kelvin-connected system, or another system that converts the output signal from DAC 104 into an output voltage or current supplied to field device 112 via VSP terminal 108. A force-sense system or Kelvin-connected system is a circuit in which separate force lines and sense lines are used to connect the load, thereby allowing accurate measurement of voltage or current by minimizing the effects of voltage drop on the power delivery lines. Output stage 106 includes a first input, a second input, a first output, a second output, and a local ground terminal (e.g., a common terminal). The first input of output stage 106 is coupled to DAC 104. The second input of output stage 106 is coupled to processing unit 102, the first output is coupled to terminal 108, and the second output is coupled to terminal 110. Output stage 106 includes a forced amplifier and two or more transconductance amplifiers for converting the output of DAC 104 from an analog signal to an analog current or voltage. The output stage provides the generated current or voltage to field device 112. The following is combined with... Figures 2 to 5 Further description of output stage 106.

[0026] VSP terminal 108 and VSN terminal 110 are screw terminals. The output of the forced amplifier in output stage 106 (e.g., a forced positive output) is provided to field device 112 via VSP terminal 108, and VSN terminal 110 is a forced negative output, which establishes a current return path to complete the circuit at local ground of output stage 106.

[0027] Figure 1 The field device 112 is a device controlled based on the output current or voltage from the programmable logic controller 101. The field device can be a sensor, actuator, valve, computing device, etc. The field device 112 includes an input stage 114 for receiving current or voltage supplied by the output stage 106. In some instances, the field device 112 may include additional components, such as an analog-to-digital converter, for converting the received analog current or voltage into a digital signal, which can be processed or used by another component of the field device 112. The input stage 114 includes a first input, a second input, and a local ground (e.g., a common terminal). As described above, the local ground voltage of the input stage may differ from the local ground voltage at the output stage 106, corresponding to common-mode mismatch. The first input of the input stage 114 is coupled to terminal 108 of the programmable logic controller 101. The second input of the input stage 114 is coupled to terminal 110.

[0028] Figure 2 It can be used for implementation Figure 1Example current output stage 200 of output stage 106. Current output stage 200 converts the analog output of DAC 104 into analog current, which is provided to field device 112 via VSP terminal 108. Current output stage 200 includes example transconductance amplifiers 202, 208, example forced amplifier 204, and example resistors 206, 210, 212.

[0029] Figure 2 A transconductance amplifier 202 amplifies the difference between the voltage provided by DAC 104 and the offset voltage provided by processing unit 102. Transconductance amplifier 202 includes a first input, a second input, a first output, and a second output. The first input (i.e., the non-inverting input) of transconductance amplifier 202 is coupled to the output of DAC 104. The second input (i.e., the inverting input) of transconductance amplifier 202 is coupled to the output of processing unit 102. The first output of transconductance amplifier 202 is coupled to the first output of transconductance amplifier 208, the first input of forced amplifier 204, and the first terminal of resistor 210. The second output of transconductance amplifier 202 is coupled to the second output of transconductance amplifier 208, the second input of forced amplifier 204, and the first terminal of resistor 212. Transconductance amplifier 202 senses the voltage difference between the output voltage of DAC 104 and the offset voltage of processing unit 102. Transconductance amplifier 202 provides current based on the voltage difference to offset the output voltage of DAC 104 based on the offset. In this way, the output current of output stage 200 corresponds to the current requirement of field device 112. The resistor R1 shown is a component of the transconductance amplifier 202 (e.g., Figure 6 The resistor 614 provides voltage amplification to improve noise and linearity. The following section combines... Figure 6 The transconductance amplifier 202 is further described.

[0030] Figure 2Forced amplifier 204 amplifies the voltage difference between its two inputs to force the voltages at both inputs to be equal by adjusting the output voltage, which in turn causes transconductance amplifier 208 to adjust the output current. Forced amplifier 204 includes a first input, a second input, and an output. The first input (i.e., the inverting input) of forced amplifier 204 is coupled to the first output of transconductance amplifier 202, the first output of transconductance amplifier 208, and the first terminal of resistor 210. The second input (i.e., the non-inverting input) of forced amplifier 204 is coupled to the second output of transconductance amplifier 202, the second output of transconductance amplifier 208, and the first terminal of resistor 212. The output of forced amplifier 204 is coupled to the second input of transconductance amplifier 208 and the first terminal of resistor 206. As described above, forced amplifier 204 forces the voltages at its first and second inputs to be equal. The voltage at the first input of forced amplifier 204 corresponds to the sum of the current supplied by the first output of transconductance amplifier 202 and the current supplied by the first output of transconductance amplifier 208. The sum of the two currents flows through resistor 210 to the common terminal, thereby generating a voltage at the first terminal of forced amplifier 204. The voltage at the second input of forced amplifier 204 corresponds to the sum of the current supplied by the second output of transconductance amplifier 202 and the current supplied by the second output of transconductance amplifier 208. The sum of the two currents flows through resistor 212 to the common terminal, thereby generating a voltage at the second terminal of forced amplifier 204. The voltage supplied by forced amplifier 204 is applied to resistor 206, thereby generating an output current corresponding to the DAC output voltage and the OFFSET signal, as shown in Equation 1 below.

[0031] (Equation 1)

[0032] In Equation 1 above, Iout is the output current of the output stage 106 supplied to the VSP terminal 108, DAC is the voltage provided by DAC 104, OFFSET is the offset voltage provided by the processing unit 102, R2 is the resistance of the resistor included in the transconductance amplifier 208, R1 is the resistance of the resistor included in the transconductance amplifier 202, and Rset is the resistance of resistor 206. Figure 2 In this example, forced amplifier 204 is a voltage amplifier. However, forced amplifier 204 could also be a current amplifier. In such an example, resistors 210 and 212 would be removed from output stage 200.

[0033] Figure 2Resistor 206 is a current-setting resistor. Resistor 206 includes a first terminal and a second terminal. The first terminal of resistor 206 is coupled to the output of forced amplifier 204 and the second input of transconductance amplifier 208. The second terminal of resistor 206 is coupled to the first input of transconductance amplifier 208 and VSP terminal 108. In some instances, resistor 206 is a variable resistor to support different current ranges. In such instances, resistor 206 may include multiple switched resistors that can be coupled or decoupled together based on control signals from processing unit 102 to change the total resistance of variable resistor 206.

[0034] Figure 2 A transconductance amplifier 208 amplifies the voltage across resistor 206, the voltage corresponding to the output voltage of forced amplifier 204 and the output current of output stage 200. Transconductance amplifier 208 includes a first input, a second input, a first output, and a second output. The first input (i.e., the non-inverting input) of transconductance amplifier 208 is coupled to the second terminal of resistor 206 and VSP terminal 108. The second input (i.e., the inverting input) of transconductance amplifier 208 is coupled to the output of forced amplifier 204 and the first terminal of resistor 206. The first output of transconductance amplifier 208 is coupled to the first output of transconductance amplifier 202, the first input of forced amplifier 204, and the first terminal of resistor 210. The second output of transconductance amplifier 208 is coupled to the second output of transconductance amplifier 202, the second input of forced amplifier 204, and the first terminal of resistor 212. Transconductance amplifier 208 senses the voltage difference across resistor 206, consistent with the high-gain forced amplifier 204. Transconductance amplifier 208 amplifies the difference to generate an output current, which serves as feedback for forced amplifier 204. Resistor R2 shown is a component of transconductance amplifier 208 (e.g., Figure 6 The resistor 614 provides voltage amplification to improve noise and linearity. The following section combines... Figure 6 The transconductance amplifier 208 is described further.

[0035] Figure 2Resistors 210 and 212 provide a path for the output current of transconductance amplifiers 202 and 208 to flow to a common terminal and generate a voltage at the input terminal of forced amplifier 204. Resistors 210 and 212 each include a first terminal and a second terminal. The first terminal of resistor 210 is coupled to the first output of transconductance amplifiers 202 and 208 and the first input of forced amplifier 204. The second terminal of resistor 210 is coupled to a common terminal (e.g., local ground) and VSN terminal 110. The first terminal of resistor 212 is coupled to the second output of transconductance amplifiers 202 and 208 and the second input of forced amplifier 204. The second terminal of resistor 212 is coupled to a common terminal (e.g., local ground) and VSN terminal 110.

[0036] Figure 3 It can be used for implementation Figure 1 Example voltage output stage 300 of output stage 106. Voltage output stage 300 converts the analog output of DAC 104 into an analog voltage, which is provided to field device 112 via VSP terminal 108. Voltage output stage 300 includes example transconductance amplifiers 302, 308, example forced amplifier 304, and example resistors 306, 310, 312.

[0037] Figure 3 The transconductance amplifier 302, the forced amplifier 304, and the resistors 306, 310, and 312 are used in conjunction with Figure 2 The transconductance amplifier 202, the forced amplifier 204, and the resistors 206, 210, and 212 operate in the same manner. Figure 3 The transconductance amplifier 308 and Figure 2 The difference with the transconductance amplifier 208 is that it senses the difference between the voltages at the VSP terminal 108 and the VSN terminal 110. Therefore, the feedback is based on the output voltage rather than the output current. Consequently, the output stage 300 outputs a voltage corresponding to the analog signal output by the DAC 104.

[0038] Figure 3The transconductance amplifier 308 amplifies the voltage difference between the voltage at VSP terminal 108 and the voltage at VSN terminal 110, which corresponds to the output voltage of the output stage 300. The transconductance amplifier 308 includes a first input, a second input, a first output, and a second output. The first input (i.e., the non-inverting input) of the transconductance amplifier 302 is coupled to the second terminal of resistor 306 and VSP terminal 108. The second input (i.e., the inverting input) of the transconductance amplifier 308 is coupled to VSN terminal 110. The first output of the transconductance amplifier 308 is coupled to the first output to the second output of the transconductance amplifier 302, the second input of the forced amplifier 304, and the first terminal of resistor 312. The second output of the transconductance amplifier 308 is coupled to the first output of the transconductance amplifier 302, the first input of the forced amplifier 304, and the first terminal of resistor 310. The transconductance amplifier 308 senses the voltage difference across VSP terminal 108 and VSN terminal 110, consistent with the high-gain forced amplifier 304. Transconductance amplifier 308 amplifies the difference to generate an output current, which serves as feedback for forced amplifier 304. (The following is in conjunction with...) Figure 6 The transconductance amplifier 308 is described further.

[0039] Figure 4 It can be used for implementation Figure 1 Example current / voltage output stage 400 of output stage 106. Current / voltage output stage 400 converts the analog output of DAC 104 into analog voltage or analog current, which is provided to field device 112 via VSP terminal 108. Current / voltage output stage 400 includes example transconductance amplifiers 402, 408, 410, example forced amplifier 404, example resistors 406, 412, 414, and example switch 416.

[0040] Figure 4 The transconductance amplifier 402, the forced amplifier 404, and the resistors 406, 412, and 414 are used in conjunction with Figure 2 Or, the transconductance amplifiers 202, 302, forced amplifiers 204, 304, and resistors 206, 210, 212, 306, 310, 312 operate in the same manner. Furthermore, the transconductance amplifier 408 operates in the same manner as... Figure 2 The transconductance amplifier 208 operates in the same manner, and the transconductance amplifier 410 operates in the same manner as the transconductance amplifier 208. Figure 3 The transconductance amplifier 308 operates in the same way. The output stage 400 will... Figure 2 Current output stage 200 and Figure 3The voltage output stage 300 is combined. Therefore, the current / voltage output stage 400 can operate as either a current output stage or a voltage output stage. Transconductance amplifiers 408 and 410 include enable terminals to enable one of the transconductance amplifiers 408 and 410 and disable the other. The enable terminals of the transconductance amplifiers 408 and 410 can be coupled to the processing unit 102. In this way, the processing unit 102 can control whether the current / voltage output stage 400 operates as either a current output stage or a voltage output stage.

[0041] Figure 4 The first output of transconductance amplifier 408 is coupled to the first output of transconductance amplifier 402, the first output of transconductance amplifier 410, the first input of forced amplifier 404, and the first terminal of resistor 414. The second output of transconductance amplifier 408 is coupled to the second output of transconductance amplifier 402, the second output of transconductance amplifier 410, the second input of forced amplifier 404, and the first terminal of resistor 412. The first output of transconductance amplifier 410 is coupled to the second output of transconductance amplifier 402, the first output of transconductance amplifier 408, the second input of forced amplifier 404, and the first terminal of resistor 412. The second output of transconductance amplifier 410 is coupled to the first output of transconductance amplifier 402, the second output of transconductance amplifier 408, the first input of forced amplifier 404, and the first terminal of resistor 414.

[0042] Figure 4 The current / voltage output stage 400 includes a switch 416. Switch 416 has a first terminal and a second terminal. The first terminal of switch 416 is coupled to the second input of transconductance amplifier 410 and VSN terminal 110. The second terminal of switch 416 is coupled to a common terminal (e.g., local ground). Switch 416 can be a transistor or other type of switch that can be opened or closed. If switch 416 is opened, an open circuit is formed. If switch 416 is closed, a closed circuit is formed to short the second input of transconductance amplifier 410 to ground. Processing unit 102 can control switch 416 (e.g., open or close). For example, if current / voltage output stage 400 is structured to operate as a current output stage, processing unit 102 can close switch 416. Furthermore, if current / voltage output stage 400 is structured to operate as a voltage output stage, processing unit 102 can open switch 416 to sense the local ground of field device 112. This allows for the application of an accurate voltage across the field device load, regardless of the local grounding of field device 112.

[0043] Figure 5 It can be used for implementation Figure 1An alternative example of the output stage 106 is a current / voltage output stage 500. The current / voltage output stage 500 converts the analog output of the DAC 104 into an analog voltage or analog current, which is provided to the field device 112 via the VSP terminal 108. The current / voltage output stage 500 includes example transconductance amplifiers 502, 508, and 510, an example forced amplifier 504, an example resistor 506, and example switches 512, 514, 516, 518, and 520.

[0044] Figure 5 Amplifier 504 is a current-input forced amplifier. Amplifier 504 includes a first input, a second input, and an output. The first input of amplifier 504 is an inverting input, which is coupled to the first output of transconductance amplifier 502, the second terminal of switch 516, and the second terminal of switch 518. The second input of amplifier 504 is a non-inverting input, which is coupled to the second output of transconductance amplifier 502, the second terminal of switch 514, and the second terminal of switch 520. The current-input amplifier 504, through its output voltage, causes transconductance amplifiers 508 and 510 to adjust the current at the input of the current-input amplifier 504 to be equal, thereby forcing the current at the input to be equal. Because Figure 5 The voltage input forced amplifier 404 is replaced by the current input amplifier 504, so it does not include resistors 412 and 414, since the resistors can be implemented within the current input amplifier 504.

[0045] Figure 5 The resistor 506 and switch 512 are used in conjunction with Figure 4 Resistor 406 and switch 416 operate in the same way. Transconductance amplifiers 502, 508, and 510 operate in the same manner as... Figure 4 The transconductance amplifiers 502, 408, and 410 operate in the same manner. However, transconductance amplifiers 508 and 510 do not include an enable terminal to enable or disable their operation. Alternatively, processing unit 102 can control switches 514, 516, 518, and 520 to enable output stage 500 to operate as a current output stage or a voltage output stage. For example, processing unit 102 can output one or more control signals to close switches 514 and 516 and open switches 518 and 520 to enable output stage 500 to operate as a current output stage. Furthermore, processing unit can output one or more control signals to open switches 514 and 516 and close switches 518 and 520 to enable output stage 500 to operate as a voltage output stage. However, if transconductance amplifiers 508 and 510 include... Figure 4 If the enable terminal is connected, switches 514, 516, 518, and 520 can be removed to replace the short circuit (e.g., wires, etching, etc.).

[0046] Figure 5 Switches 514, 516, 518, and 520 each include a first terminal and a second terminal. The first terminal of switch 514 is coupled to the first output of transconductance amplifier 508. The second terminal of switch 514 is coupled to the first output of transconductance amplifier 502, the first input of current-input forced amplifier 504, and the second terminal of switch 518. The first terminal of switch 516 is coupled to the second output of transconductance amplifier 508. The second terminal of switch 516 is coupled to the second output of transconductance amplifier 502, the second input of current-input forced amplifier 504, and the second terminal of switch 520. The first terminal of switch 518 is coupled to the second output of transconductance amplifier 510. The second terminal of switch 520 is coupled to the first output of transconductance amplifier 502, the second terminal of switch 514, and the second input of forced amplifier 504. Switches 514, 516, 518, and 520 may be implemented by one or more transistors, multiplexers, or other circuit systems.

[0047] Figure 6 It can be used for implementation Figures 2 to 5 Example transconductance amplifier 600 includes transconductance amplifiers 202, 208, 302, 308, 402, 408, 410, 502, 508, and 510. Transconductance amplifier 600 includes example sense amplifiers 602 and 608, example transistors 604 and 610, example current sources 606 and 612, example resistor 614, and example switches 616 and 618.

[0048] Figure 6The sense amplifier 602 is an amplifier that generates an output voltage, which is an amplification of the voltage difference between the two inputs of the amplifier 602. The sense amplifier 602 includes a first input (e.g., an inverting input), a second input (e.g., a non-inverting input), and an output. The first input of the sense amplifier is coupled to a first current terminal of transistor 604, a second terminal of current source 606, and a first terminal of resistor 614. The second input of the sense amplifier 602 is coupled to a first input of transconductance amplifier 600. Therefore, if transconductance amplifier 600 implements transconductance amplifiers 202, 302, 402, and 502, the second input of the sense amplifier 602 is coupled to DAC 104. If transconductance amplifier 600 implements transconductance amplifiers 208, 308, 408, 410, 508, and 510, the second input of the sense amplifier 602 is coupled to the second terminals of resistors 206, 306, 406, and 506 and VSP terminal 108. The output of the sense amplifier 602 is coupled to a control terminal of transistor 604. Amplifier 602 outputs a voltage that amplifies the difference between the two input voltages. The output voltage of amplifier 602 is used to force the voltages at the two inputs to be equal, as further described below.

[0049] Output control based on sensing amplifier 602 Figure 6The transistor 604 includes a first current terminal (e.g., a source terminal), a second current terminal (e.g., a drain terminal), and a control terminal (e.g., a gate terminal). The first current terminal of transistor 604 is coupled to a first input of sense amplifier 602, a second terminal of current source 606, and a first terminal of resistor 614. The second current terminal of transistor 604 is coupled to a first output of transconductance amplifier 600. Therefore, if transconductance amplifiers 202, 302, 402, and 502 are implemented, the first current terminal of transistor 604 is coupled to one or more of forced amplifiers 204, 304, 404, and 504, transconductance amplifiers 208, 308, 408, 410, 508, and 510, or resistors 412 and 414. If transconductance amplifiers 208, 308, 408, 410, 508, and 510 are implemented, the first current terminal of transistor 604 is coupled to one or more of the forced amplifiers 204, 304, 404, and 504, transconductance amplifiers 202, 208, 302, 308, 402, 408, 410, 502, 508, and 510, or resistors 412 and 414. The control terminal of transistor 604 is coupled to the output of sense amplifier 602. Transistor 604 is a p-channel metal-oxide-semiconductor field-effect transistor (PMOS, p-channel MOSFET, etc.). However, transistor 604 may be implemented by another type of transistor. If the voltage supplied by sense amplifier 602 is higher than a threshold, transistor 604 prevents current from flowing to the first output. If the voltage supplied by sense amplifier 602 is lower than a threshold, transistor 604 allows at least some current to flow out of the first output. The amount of current allowed by transistor 604 may be based on the amount of voltage supplied by sense amplifier 602.

[0050] Figure 6 A current source 606 provides current (e.g., a predefined or preset amount) to the nodes corresponding to the first input of the sense amplifier 602, the first terminal of the resistor 614, and the first current terminal of the transistor 604. The current source has an input and an output. The input of the current source 606 is coupled to the second terminal of the switch 616. The output of the current source 606 is coupled to the first input of the sense amplifier 602, the first terminal of the resistor 614, and the first current terminal of the transistor 604. If the switch 616 is closed, the current source 606 provides current at the output terminal using the power supply terminal. The amount of current provided by the current source 606 is the same as or substantially similar to the current provided by the current source 612.

[0051] Figure 6The sensing amplifier 608 is an amplifier that generates an output voltage, which is an amplification of the voltage difference between the two inputs of the amplifier 608. The sensing amplifier 608 includes a first input (e.g., an inverting input), a second input (a non-inverting input), and an output. The first input of the sensing amplifier is an inverting input, coupled to a first current terminal of transistor 610, a second terminal of current source 612, and a second terminal of resistor 614. The second input of the sensing amplifier 608 is coupled to a second input of transconductance amplifier 600. Therefore, if transconductance amplifier 600 implements transconductance amplifiers 202, 302, 402, and 502, the second input of the sensing amplifier 608 is coupled to processing unit 102 to obtain an offset signal. If transconductance amplifier 600 implements transconductance amplifiers 208, 408, and 508, the second input of the sensing amplifier 608 is coupled to a first terminal of resistors 206, 306, 406, and 506. If transconductance amplifier 600 implements transconductance amplifiers 308, 410, and 510, then the second input of sensing amplifier 608 is coupled to one or more of VSN terminal 110 or switch 416. The output of sensing amplifier 608 is coupled to the control terminal of transistor 610. Amplifier 608 outputs a voltage as an amplified difference between the two input voltages. Amplifier 608 output voltage is used to force the voltages at the two inputs to be equal, as further described below.

[0052] Output control based on sensing amplifier 608 Figure 6The transistor 610 includes a first current terminal (e.g., a source terminal), a second current terminal (e.g., a drain terminal), and a control terminal (e.g., a gate terminal). The first current terminal of transistor 610 is coupled to a first input of sense amplifier 608, a second terminal of current source 612, and a second terminal of resistor 614. The second current terminal of transistor 610 is coupled to a second output of transconductance amplifier 600. Therefore, if transconductance amplifiers 202, 302, 402, and 502 are implemented, the first current terminal of transistor 610 is coupled to one or more of forced amplifiers 204, 304, 404, and 504, transconductance amplifiers 208, 308, 408, 410, 508, and 510, or resistors 412 and 414. If transconductance amplifiers 208, 308, 408, 410, 508, and 510 are implemented, the first current terminal of transistor 610 is coupled to one or more of forced amplifiers 204, 304, 404, and 504, transconductance amplifiers 202, 208, 302, 308, 402, 408, 410, 502, 508, and 510, or resistors 412 and 414. The control terminal of transistor 610 is coupled to the output of sense amplifier 608. Transistor 610 is a p-channel metal-oxide-semiconductor field-effect transistor (PMOS, p-channel MOSFET, etc.). However, transistor 610 may be implemented by another type of transistor. If the voltage supplied by sense amplifier 608 is higher than a threshold, transistor 610 prevents current from flowing to the second output. If the voltage supplied by sense amplifier 608 is lower than a threshold, transistor 610 allows at least some current to flow through the second output. The amount of current allowed by transistor 610 may be based on the amount of voltage supplied by sense amplifier 608.

[0053] Figure 6 A current source 612 provides current (e.g., a predefined or preset amount) to the nodes corresponding to the first input of the sense amplifier 608, the second terminal of the resistor 614, and the first current terminal of the transistor 610. The current source has an input and an output. The input of the current source 612 is coupled to the second terminal of the switch 616. The output of the current source 612 is coupled to the first input of the sense amplifier 608, the second terminal of the resistor 614, and the first current terminal of the transistor 610. If the switch 616 is closed, the current source 612 provides current at the output terminal using the power supply terminal. The amount of current provided by the current source 612 is the same as or substantially similar to the current supplied by the current source 612.

[0054] Figure 6Resistor 614 forms a resistive path from one side of transconductance amplifier 600 to the other side of transconductance amplifier 600. Resistor 614 includes a first terminal and a second terminal. The first terminal of resistor 614 is coupled to the first input of sense amplifier 602, the first current terminal of transistor 604, and the output of current source 606. The second terminal of resistor 614 is coupled to the first input of sense amplifier 608, the first current terminal of transistor 610, and the output of current source 612. If the voltage at the first terminal of resistor 614 is the same as the voltage at the second terminal of resistor 614, there is no voltage difference across resistor 614. Therefore, no current flows between the terminals of resistor 614. If the voltage at the first terminal of resistor 614 is different from the voltage at the second terminal of resistor 614, some current flows through the terminals of resistor 614. Amplifiers 602 and 608 track the IN1 and IN2 voltages, thereby ensuring the voltage difference across resistor 614, which achieves high linearity, low noise, and high CMRR.

[0055] Figure 6 Switch 616 connects or disconnects the power supply terminal from the input of current source 606. Switch 616 includes a first terminal and a second terminal. The first terminal of switch 616 is coupled to the power supply terminal. The second terminal of switch 616 is coupled to the input of current source 606. Processing unit 102 can output a control signal to open or close switch 616, thereby enabling or disabling the use of transconductance amplifier 600. For example, for Figure 4 The processing unit 102 can configure the output stage 400 to operate as a current output stage or a voltage output stage, depending on which transconductance amplifier 408 or 410 is enabled. Therefore, the processing unit 102 can use switch 616 to enable the transconductance amplifier 600. Switch 616 can be implemented by one or more transistors, multiplexers, or any other circuitry.

[0056] Figure 6 Switch 618 connects or disconnects the power supply terminal from the input of current source 612. Switch 618 includes a first terminal and a second terminal. The first terminal of switch 618 is coupled to the power supply terminal. The second terminal of switch 618 is coupled to the input of current source 612. Processing unit 102 can output a control signal to open or close switch 618, thereby enabling or disabling the use of transconductance amplifier 600. For example, for Figure 4 The processing unit 102 can configure the output stage 400 to operate as a current output stage or a voltage output stage, depending on which transconductance amplifier 408 or 410 is enabled. Therefore, the processing unit 102 can use switch 618 to enable the transconductance amplifier 600. Switch 618 can be implemented by one or more transistors, multiplexers, or any other circuit system. In some instances, switches 616 and 618 can... Figure 6 circuit or Figures 2 to 5 Implemented in different parts of the circuit to enable voltage output and disable current output, or vice versa. For example, Figure 5 Includes switches 514, 516, 518, and 520. Therefore, it can be obtained from... Figure 5 Circuit 500 removes switches 616 and 618. Alternatively, switches 616 and 618 may be implemented at the outputs (e.g., out1 and out2) / second current terminals of transistors 604 and 610 to prevent the outputs from being disconnected or shorted from the rest of the circuit.

[0057] In operation, a first voltage is applied to the first input of transconductance amplifier 600 (e.g., the second input of sensing amplifier 602). Furthermore, a second voltage is applied to the second input of transconductance amplifier 600 (e.g., the second input of sensing amplifier 608). As described above, amplifiers 602 and 608 generate outputs to force the inputs to have the same voltage. Therefore, the output voltage of sensing amplifier 602 forces the voltage at the first terminal of resistor 614 to be the first voltage, and the output voltage of sensing amplifier 608 forces the voltage at the second terminal of resistor 614 to be the second voltage. If the first voltage equals the second voltage, there is no voltage drop across resistor 614. Therefore, no current or only a very small amount of current flows through resistor 614. Furthermore, no current or only a very small amount of current flows to the inputs of sensing amplifiers 602 and 608 because amplifiers 602 and 608 have high or infinite input impedance. Therefore, at the first output, all current from current source 606 is supplied via the current terminal of transistor 604, and at the second output, all current from current source 612 is supplied via the current terminal of transistor 610. Because current sources 606 and 612 output the same current, if the input voltage is the same, the output terminals will output the same current.

[0058] If the first voltage is higher than the second voltage, a voltage difference exists across the first and second terminals of resistor 614. Therefore, at least some of the current from current source 606 flows out of the second output via the current terminal of transistor 610. Consequently, the amount of current output from the first output terminal is less than the amount of current output from the second output terminal. If the first voltage is lower than the second voltage, a voltage difference exists across the first and second terminals of resistor 614. Therefore, at least some of the current from current source 612 flows out of the first output via the current terminal of transistor 604. Consequently, the amount of current output from the second output terminal is less than the amount of current output from the first output terminal.

[0059] Figure 7Example graph 700 shows the CMRR results using the example described herein. The x-axis of graph 700 is CMRR, and the y-axis of graph 700 is the number of samples that produced a specific CMRR. Graph 700 includes samples acquired at different temperatures (e.g., -40°C, 27°C, and 125°C). As shown in example graph 700, all samples produced a CMRR greater than 134.5 dB without trimming. Graph 700 shows that, based on testing, the average CMRR from 90 samples is 152.676 dB with a standard deviation of 9.27. The output stage of INA produces a CMRR of approximately 80 dB. Therefore, the example described herein has a CMRR more than two orders of magnitude higher. Furthermore, ideally, the current output impedance of the output stage is sufficiently high. For example, some standards or customers may require a current output impedance of more than 100 megohms for proper operation. Based on testing, the current output impedance of the output stage described herein is at least more than 450 megohms, far exceeding the 100 megohm requirement. The average measured output impedance for the output stage test described in this paper is 61.23 gigahertz, with a standard deviation of 61.23 gigahertz, and the maximum measured output impedance is 554.1 gigahertz.

[0060] Figures 2 to 6 The implementation is shown in the figure. Figure 1 One or more example ways to output level 106. However, Figures 1 to 6 One or more of the elements, processes or apparatus shown may be combined, divided, rearranged, omitted, eliminated or implemented in any other way.

[0061] Furthermore, the output stage 106 may be implemented by one or more analog or digital circuits, logic circuits, programmable processors, programmable controllers, graphics processing units (GPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable logic devices (PLDs), or field-programmable logic devices (FPLDs).

[0062] When reading any device or system technical solution of this patent to cover purely software or firmware implementations, output stage 106 is hereby expressly defined as comprising a non-transient computer-readable storage device or storage disk, such as a memory, digital versatile disc (DVD), optical disc (CD), Blu-ray disc, etc., comprising software or firmware. Furthermore, controller circuitry system 230 may, in addition to Figures 2 to 6The invention may include, or replace, one or more elements, processes, or devices shown, or may include more than one of any or all of the elements, processes, and devices shown. As used herein, the phrase “communication” includes its variations, encompassing direct communication or indirect communication through one or more intermediate components, and not requiring direct physical (e.g., wired) communication or continuous communication, but also including selective communication carried out at one or more of periodic intervals, scheduled intervals, non-periodic intervals, or one-off events.

[0063] While certain example methods, apparatuses, and articles of manufacture have been described herein, the scope of this patent is not limited thereto. Rather, this patent covers all methods, apparatuses, and articles of manufacture that fall entirely within the scope of the claims of this patent.

[0064] The descriptive terms “first,” “second,” “third,” etc., are used herein to identify multiple elements or components that may refer to separately. Unless otherwise specified or known from the context of their use, these descriptive terms do not imply any priority, physical order, or arrangement or chronological order in a list, but are merely labels to refer to multiple elements or components separately to facilitate understanding of the described instance. In some examples, the descriptive term “first” may be used to refer to an element in a particular embodiment, while the same element may be referred to in the claims by different descriptive terms such as “second” or “third.” In such cases, these descriptive terms are used solely for ease of reference to multiple elements or components.

[0065] In this specification and claims, unless otherwise stated, the terms "comprising" and "having," and their variations, are included in a manner similar to the term "comprising." Unless otherwise stated, "about," "approximately," or "substantially" preceding a value means + / - 10% of the stated value. In another instance, "about," "approximately," or "substantially" preceding a value means + / - 5% of the stated value. In yet another instance, "about," "approximately," or "substantially" preceding a value means + / - 1% of the stated value.

[0066] As used herein, the terms “coupled,” “couples,” and variations thereof may cover a connection, communication, or signal path that achieves a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then: if a first example device A is coupled to device B; or if a second example device A is coupled to device B via an intermediate component C, provided that the intermediate component C does not substantially alter the functional relationship between device A and device B, such that device B is controlled by device A via a control signal generated by device A. Furthermore, the terms “coupled,” “couples,” and variations thereof include indirect or direct electrical or mechanical connections.

[0067] A device “configured” to perform a task or function may be configured (e.g., programmed or hardwired at least one) to perform the function during manufacturing by the manufacturer, or may be configured (or reconfigured) by the user after manufacturing to perform the function or other additional or alternative functions. The configuration may be achieved through at least one firmware or software program of the device, through the construction or layout of the device’s hardware components and interconnects, or a combination thereof.

[0068] Despite Figures 1 to 6 Not all components are separately labeled, but the components or elements of the systems and circuits shown herein have one or more conductors or ends that allow signals to enter or exit the component or element. Conductors or ends (or portions thereof) may be referred to herein as pins, pads, terminals (e.g., including input terminals, output terminals, reference terminals, and ground terminals), inputs, outputs, nodes, and interconnects.

[0069] As used herein, a “terminal” of a component, device, system, circuit, integrated circuit, or other electronic or semiconductor component is typically a conductor, such as a wire, trace, pin, pad, or other connector or interconnect that enables the component, device, system, etc., to be electrically or mechanically connected to another component, device, system, etc. Terminals can be used, for example, to receive or provide analog or digital electrical signals (or simply signals), or for electrical connection to a common or ground reference. Thus, an input terminal or input is used to receive signals from another component, device, system, etc. An output terminal or output is used to provide signals to another component, device, system, etc. Other terminals can be used to connect to a common, ground, or voltage reference, such as a reference terminal or ground terminal. Terminals on an IC or PCB may also be referred to as pins (longitudinal conductors) or pads (planar conductors). A node is a connection point or interconnect of two or more terminals. An example number of terminals and nodes may be shown. However, depending on the specific circuit system or system topology, there may be more or fewer terminals and nodes. However, in some cases, the terms “terminal,” “node,” “interconnect,” “pad,” and “pin” are used interchangeably.

[0070] The term “or” when used in the form of, for example, A, B or C, refers to any combination or subset of A, B, C, such as (1) only A, (2) only B, (3) only C, (4) A and B, (5) A and C, (6) B and C, or (7) A and B and C.

[0071] As used herein, a “programmable circuit system” is defined as comprising at least one of the following: (i) one or more special-purpose circuits (e.g., application-specific integrated circuits (ASICs)) that are structured to perform specific operations and comprise one or more semiconductor-based logic devices (e.g., electrical hardware implemented by one or more transistors), or (ii) one or more general-purpose semiconductor-based circuits that can be programmed with instructions to perform one or more specific functions or operations and comprise one or more semiconductor-based logic devices (e.g., electrical hardware implemented by one or more transistors). Examples of programmable circuit systems include programmable microprocessors, such as: a central processing unit (CPU) that can execute a first instruction to perform one or more operations or functions; a field-programmable gate array (FPGA) that can be programmed with a second instruction to configure or structure at least one of the FPGAs, thereby instantiating one or more operations or functions corresponding to the first instruction; a graphics processing unit (GPU) that can execute the first instruction to perform one or more operations or functions; a digital signal processor (DSP) that can execute the first instruction to perform one or more operations or functions; an XPU; a network processing unit (NPU); one or more microcontrollers that can execute the first instruction to perform one or more operations or functions; or an integrated circuit, such as an application-specific integrated circuit (ASIC). For example, an XPU can be implemented by a heterogeneous computing system that includes a variety of programmable circuit systems (e.g., one or more FPGAs, one or more CPUs, one or more GPUs, one or more NPUs, one or more DSPs, etc., and any combination thereof) and configuration technologies (e.g., application programming interfaces (APIs)) that can distribute computing tasks to any or more of the various types of programmable circuit systems that are suitable and can be used to perform computing tasks.

[0072] As used herein, an integrated circuit / circuit system is defined as one or more semiconductor packages containing one or more circuit elements, such as transistors, capacitors, inductors, resistors, current paths, diodes, etc. For example, an integrated circuit can be implemented as one or more of an ASIC, FPGA, chip, microchip, programmable circuit system, semiconductor substrate coupling multiple circuit elements, system-on-a-chip (SoC), etc.

[0073] As used herein, the terms “terminal,” “node,” “interconnect,” “pin,” and “lead” are used interchangeably. Unless specifically stated otherwise, these terms are generally used to refer to interconnections or ends between device elements, circuit elements, integrated circuits, devices, or other electronic or semiconductor components.

[0074] In this specification and claims, the described "circuit system" may include one or more circuits. A circuit or device described herein as including certain components may alternatively be adapted to be coupled to those components used to form the described circuit system or device. For example, a structure described as including one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., one or a combination of resistors, capacitors, or inductors), or one or more sources (e.g., voltage sources or current sources) may alternatively include only semiconductor elements within a single physical device (e.g., at least one in a semiconductor die or integrated circuit (IC) package) and may be adapted to be coupled, during or after manufacturing, for example by at least one of an end user or a third party, to at least some of the passive elements or sources to form the described structure.

[0075] The circuits described herein can be reconfigured to include the replaced components, thereby providing functionality at least partially similar to that available before the component replacement. Unless otherwise stated, components shown as resistors generally represent any one or more elements coupled in at least one of series or parallel to provide the amount of impedance represented by the resistor shown. For example, a resistor or capacitor shown and described herein as a single component may alternatively be multiple resistors or capacitors coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may alternatively be multiple resistors or capacitors coupled in series between the same two nodes as the single resistor or capacitor. While some elements in the described examples are included in the integrated circuit and others are outside the integrated circuit, in other example embodiments, additional or fewer features may be incorporated into the integrated circuit. Additionally, some or all features shown as outside the integrated circuit may be included in the integrated circuit, and some features shown as inside the integrated circuit may be incorporated outside the integrated circuit. As used herein, the term "integrated circuit" means one or more circuits that are at least one of the following: (i) incorporated in / above a semiconductor substrate; (ii) incorporated in a single semiconductor package; (iii) incorporated in the same module; or (iv) incorporated in / on the same printed circuit board.

[0076] This document describes example methods, devices, systems, and articles of art corresponding to the output stage of a digital-to-analog converter. Other examples and combinations thereof include the following: Example 1 includes a device comprising: a first transconductance amplifier having a first output and a second output; an amplifier having a first input, a second input, and an output, the first input of the amplifier being coupled to the first output of the first transconductance amplifier, and the second input of the amplifier being coupled to the second output of the first transconductance amplifier; a resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the output of the amplifier; and a second transconductance amplifier having a first input, a second input, a first output, and a second output, the first input of the second transconductance amplifier being coupled to the second terminal of the resistor, the second input of the second transconductance amplifier being coupled to the output of the amplifier and the first terminal of the resistor, the first output of the second transconductance amplifier being coupled to the first output of the first transconductance amplifier and the first input of the amplifier, and the second output of the second transconductance amplifier being coupled to the second output of the first transconductance amplifier and the second input of the amplifier.

[0077] Example 2 includes the device according to Example 1, wherein the resistor is a first resistor, and the device further includes: a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to a first output of a first transconductance amplifier, a first input of the amplifier, and a first output of a second transconductance amplifier, and the second terminal of the second resistor being coupled to a common terminal; and a third resistor having a first terminal and a second terminal, the first terminal of the third resistor being coupled to a second output of the first transconductance amplifier, a second input of the amplifier, and a second output of the second transconductance amplifier, and the second terminal of the third resistor being coupled to the common terminal.

[0078] Example 3 includes the device according to Example 1, wherein the first transconductance amplifier further has a first input and a second input, the device further includes: a digital-to-analog converter (DAC) having an input and an output, the output of the DAC being coupled to the first input of the first transconductance amplifier; and a processor having a first output and a second output, the first output of the processor being coupled to the input of the DAC, and the second output of the processor being coupled to the second input of the first transconductance amplifier.

[0079] Example 4 includes the device according to Example 1, wherein the resistor is a first resistor, and the second transconductance amplifier includes: a first sensing amplifier having a first input, a second input, and an output, the second input being the first input of the second transconductance amplifier; a first transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the first transistor being coupled to the second input of the first sensing amplifier, the second current terminal of the first transistor being the first output of the second transconductance amplifier, and the control terminal of the first transistor being coupled to the output of the first sensing amplifier; and a second sensing amplifier having a first input, a second input, and an output, the second input being the first input of the transconductance amplifier. The second input; a second transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the second transistor being coupled to the first input of the second sense amplifier, the second current terminal of the first transistor being the second output of the second transconductance amplifier, and the control terminal of the second transistor being coupled to the output of the second sense amplifier; and a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first current terminal of the first transistor and the first input of the first sense amplifier, and the second terminal of the second resistor being coupled to the first current terminal of the second transistor and the first input of the second sense amplifier.

[0080] Example 5 includes the device according to Example 4, wherein the second transconductance amplifier further includes: a first current source having an output, the output of the first current source being coupled to a first current terminal of the first transistor, a first input of the first sense amplifier, and a first terminal of the second resistor; and a second current source having an output, the output of the second current source being coupled to the first current terminal of the second transistor, the first input of the second sense amplifier, and a second terminal of the second resistor.

[0081] Example 6 includes the device according to Example 5, wherein the first current source has an input and the second current source has an input, and the second transconductance amplifier further includes: a first switch having a first terminal, a second terminal and a control terminal, the first terminal of the first switch being coupled to a power supply terminal and the second terminal of the first switch being coupled to the input of the first current source; and a second switch having a first terminal, a second terminal and a control terminal, the first terminal of the second switch being coupled to the power supply terminal and the second terminal of the second switch being coupled to the input of the second current source.

[0082] Example 7 includes the device according to Example 1, wherein the first input of the first transconductance amplifier is a non-inverting input, the second input of the transconductance amplifier is an inverting input, the first input of the amplifier is an inverting input, the second input of the amplifier is a non-inverting input, the first input of the second transconductance amplifier is a non-inverting input, and the second input of the second transconductance amplifier is an inverting input.

[0083] Example 8 includes a device comprising: a positive voltage power supply terminal; a negative voltage power supply terminal; a first transconductance amplifier having a first output and a second output; an amplifier having a first input, a second input, and an output, the first input of the amplifier being coupled to the first output of the first transconductance amplifier, and the second input of the amplifier being coupled to the second output of the first transconductance amplifier; a resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the output of the amplifier; and a second transconductance amplifier having a first input, a second input, a first output, and a second output, the first input of the second transconductance amplifier being coupled to the second terminal of the resistor and the positive voltage power supply terminal, the second input of the second transconductance amplifier being coupled to the negative voltage power supply terminal, the first output of the second transconductance amplifier being coupled to the first output of the first transconductance amplifier and the first input of the amplifier, and the second output of the second transconductance amplifier being coupled to the second output of the first transconductance amplifier and the second input of the amplifier.

[0084] Example 9 includes the device according to Example 8, wherein the resistor is a first resistor, and the device further includes: a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to a first output of a first transconductance amplifier, a first input of the amplifier, and a first output of a second transconductance amplifier, and the second terminal of the second resistor being coupled to a common terminal; and a third resistor having a first terminal and a second terminal, the first terminal of the third resistor being coupled to a second output of the first transconductance amplifier, a second input of the amplifier, and a second output of the second transconductance amplifier, and the second terminal of the third resistor being coupled to the common terminal.

[0085] Example 10 includes the device according to Example 8, wherein the first transconductance amplifier further has a first input and a second input, the device further includes: a digital-to-analog converter (DAC) having an input and an output, the output of the DAC being coupled to the first input of the first transconductance amplifier; and a processor having a first output and a second output, the first output of the processor being coupled to the input of the DAC, and the second output of the processor being coupled to the second input of the first transconductance amplifier.

[0086] Example 11 includes the device according to Example 8, wherein the resistor is a first resistor, and the second transconductance amplifier includes: a first sensing amplifier having a first input, a second input, and an output, the second input being the first input of the second transconductance amplifier; a first transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the first transistor being coupled to the second input of the first sensing amplifier, the second current terminal of the first transistor being the first output of the second transconductance amplifier, and the control terminal of the first transistor being coupled to the output of the first sensing amplifier; and a second sensing amplifier having a first input, a second input, and an output, the second input being the first input of the transconductance amplifier. The second input; a second transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the second transistor being coupled to the first input of the second sense amplifier, the second current terminal of the first transistor being the second output of the second transconductance amplifier, and the control terminal of the second transistor being coupled to the output of the second sense amplifier; and a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first current terminal of the first transistor and the first input of the first sense amplifier, and the second terminal of the second resistor being coupled to the first current terminal of the second transistor and the first input of the second sense amplifier.

[0087] Example 12 includes the device according to Example 11, wherein the second transconductance amplifier further includes: a first current source having an output, the output of the first current source being coupled to a first current terminal of the first transistor, a first input of the first sense amplifier, and a first terminal of the second resistor; and a second current source having an output, the output of the second current source being coupled to the first current terminal of the second transistor, the first input of the second sense amplifier, and a second terminal of the second resistor.

[0088] Example 13 includes the device according to Example 12, wherein the first current source has an input and the second current source has an input, and the second transconductance amplifier further includes: a first switch having a first terminal, a second terminal and a control terminal, the first terminal of the first switch being coupled to a power supply terminal and the second terminal of the first switch being coupled to the input of the first current source; and a second switch having a first terminal, a second terminal and a control terminal, the first terminal of the second switch being coupled to the power supply terminal and the second terminal of the second switch being coupled to the input of the second current source.

[0089] Example 14 includes the device according to Example 8, wherein the first input of the first transconductance amplifier is a non-inverting input, the second input of the transconductance amplifier is an inverting input, the first input of the amplifier is an inverting input, the second input of the amplifier is a non-inverting input, the first input of the second transconductance amplifier is a non-inverting input, and the second input of the second transconductance amplifier is an inverting input.

[0090] Example 15 includes a device comprising: a first switch having a first terminal and a second terminal; a second switch having a first terminal and a second terminal; a third switch having a first terminal and a second terminal; a fourth switch having a first terminal and a second terminal; a fifth switch having a first terminal and a second terminal, the second terminal being coupled to a common terminal; a first transconductance amplifier having a first output and a second output, the first output of the first transconductance amplifier being coupled to the second terminal of the second switch and the second terminal of the third switch, the second output of the first transconductance amplifier being coupled to the second terminal of the first switch and the second terminal of the fourth switch; an amplifier having a first input, a second input, and an output, the first input of the amplifier being coupled to the first output of the first transconductance amplifier, the second terminal of the second switch, and the second terminal of the third switch, the second input of the amplifier being coupled to the second output of the first transconductance amplifier, the second terminal of the first switch, and the second terminal of the fourth switch; and a resistor having a first terminal and a... The second terminal, the first terminal of the resistor is coupled to the output of the amplifier; and the second transconductance amplifier having a first input, a second input, a first output and a second output, the first input of the second transconductance amplifier being coupled to the second terminal of the resistor, the second input of the second transconductance amplifier being coupled to the output of the amplifier and the first terminal of the resistor, the first output of the second transconductance amplifier being coupled to the first terminal of the first switch, the second output of the second transconductance amplifier being coupled to the first terminal of the second switch; and the third transconductance amplifier having a first input, a second input, a first output and a second output, the first input of the third transconductance amplifier being coupled to the second terminal of the resistor and the first input of the second transconductance amplifier, the second input of the third transconductance amplifier being coupled to the first terminal of the fifth switch, the first output of the third transconductance amplifier being coupled to the first terminal of the fourth switch, and the second output of the third transconductance amplifier being coupled to the first terminal of the third switch.

[0091] Example 16 includes the device according to Example 15, wherein the amplifier is a current input amplifier.

[0092] Example 17 includes the device according to Example 15, wherein the first transconductance amplifier further has a first input and a second input, the device further comprising: a digital-to-analog converter (DAC) having an input and an output, the output of the DAC being coupled to the first input of the first transconductance amplifier; and a processor having a first output and a second output, the first output of the processor being coupled to the input of the DAC, and the second output of the processor being coupled to the second input of the first transconductance amplifier.

[0093] Example 18 includes the device according to Example 15, wherein the resistor is a first resistor, and the second transconductance amplifier includes: a first sensing amplifier having a first input, a second input, and an output, the second input being the first input of the second transconductance amplifier; a first transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the first transistor being coupled to the second input of the first sensing amplifier, the second current terminal of the first transistor being the first output of the second transconductance amplifier, and the control terminal of the first transistor being coupled to the output of the first sensing amplifier; and a second sensing amplifier having a first input, a second input, and an output, the second input being the transconductance amplifier. The second input; a second transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the second transistor being coupled to the first input of the second sense amplifier, the second current terminal of the first transistor being the second output of the second transconductance amplifier, the control terminal of the second transistor being coupled to the output of the second sense amplifier; and a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first current terminal of the first transistor and the first input of the first sense amplifier, the second terminal of the second resistor being coupled to the first current terminal of the second transistor and the first input of the second sense amplifier.

[0094] Example 19 includes the device according to Example 18, wherein the second transconductance amplifier further comprises: a first current source having an input and an output, the input of the first current source being coupled to a power supply terminal, the output of the first current source being coupled to a first current terminal of the first transistor, a first input of the first sense amplifier, and a first terminal of the second resistor; and a second current source having an input and an output, the input of the second current source being coupled to the power supply terminal, the output of the second current source being coupled to the first current terminal of the second transistor, the first input of the second sense amplifier, and a second terminal of the second resistor.

[0095] Example 20 includes the device according to Example 18, wherein the first input of the first transconductance amplifier is a non-inverting input, the second input of the transconductance amplifier is an inverting input, the first input of the amplifier is an inverting input, the second input of the amplifier is a non-inverting input, the first input of the second transconductance amplifier is a non-inverting input, the second input of the second transconductance amplifier is an inverting input, the first input of the third transconductance amplifier is a non-inverting input, and the second input of the third transconductance amplifier is an inverting input.

[0096] As should be understood from the foregoing, example systems, apparatuses, articles, and methods corresponding to the output stage of a digital-to-analog converter have been described. The described systems, apparatuses, articles, and methods enable the output stage to have increased CMRR, low noise, and high linearity without requiring large, complex, or expensive components, or complex and costly trimmings. Therefore, the described systems, apparatuses, articles, and methods relate to one or more improvements in the operation of machines such as computers or other electronic devices.

[0097] Modifications to the described examples are possible within the scope of the claims, and other examples are also possible.

Claims

1. An apparatus comprising: A first transconductance amplifier having a first output and a second output; An amplifier having a first input, a second input, and an output, wherein the first input of the amplifier is coupled to the first output of a first transconductance amplifier, and the second input of the amplifier is coupled to the second output of the first transconductance amplifier; A resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the output of the amplifier; as well as A second transconductance amplifier has a first input, a second input, a first output, and a second output. The first input of the second transconductance amplifier is coupled to the second terminal of the resistor. The second input of the second transconductance amplifier is coupled to the output of the amplifier and the first terminal of the resistor. The first output of the second transconductance amplifier is coupled to the first output of the first transconductance amplifier and the first input of the amplifier. The second output of the second transconductance amplifier is coupled to the second output of the first transconductance amplifier and the second input of the amplifier.

2. The device of claim 1, wherein the resistor is a first resistor, and the device further comprises: A second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first output of the first transconductance amplifier, the first input of the amplifier, and the first output of the second transconductance amplifier, and the second terminal of the second resistor being coupled to a common terminal; and A third resistor has a first terminal and a second terminal, the first terminal of the third resistor being coupled to the second output of the first transconductance amplifier, the second input of the amplifier and the second output of the second transconductance amplifier, and the second terminal of the third resistor being coupled to the common terminal.

3. The device of claim 1, wherein the first transconductance amplifier further has a first input and a second input, and the device further comprises: A digital-to-analog converter (DAC) having an input and an output, the output of the DAC being coupled to the first input of a first transconductance amplifier; and A processor having a first output and a second output, the first output of the processor being coupled to the input of the DAC, and the second output of the processor being coupled to the second input of the first transconductance amplifier.

4. The device of claim 1, wherein the resistor is a first resistor, and the second transconductance amplifier comprises: A first sensing amplifier has a first input, a second input, and an output, wherein the second input is the first input of the second transconductance amplifier; A first transistor has a first current terminal, a second current terminal, and a control terminal. The first current terminal of the first transistor is coupled to the second input of the first sensing amplifier, the second current terminal of the first transistor is the first output of the second transconductance amplifier, and the control terminal of the first transistor is coupled to the output of the first sensing amplifier. The second sensing amplifier has a first input, a second input, and an output, wherein the second input is the second input of the transconductance amplifier; The second transistor has a first current terminal, a second current terminal, and a control terminal. The first current terminal of the second transistor is coupled to the first input of the second sense amplifier, the second current terminal of the first transistor is the second output of the second transconductance amplifier, and the control terminal of the second transistor is coupled to the output of the second sense amplifier. as well as A second resistor has a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first current terminal of the first transistor and the first input of the first sensing amplifier, and the second terminal of the second resistor being coupled to the first current terminal of the second transistor and the first input of the second sensing amplifier.

5. The device of claim 4, wherein the second transconductance amplifier further comprises: A first current source having an output, the output of the first current source being coupled to a first current terminal of a first transistor, a first input of a first sense amplifier, and a first terminal of a second resistor; and A second current source having an output, the output of the second current source being coupled to the first current terminal of the second transistor, the first input of the second sense amplifier, and the second terminal of the second resistor.

6. The device of claim 5, wherein the first current source has an input, and the second current source has an input, and the second transconductance amplifier further comprises: A first switch having a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first switch is coupled to a power supply terminal, and the second terminal of the first switch is coupled to the input of the first current source; and The second switch has a first terminal, a second terminal and a control terminal, wherein the first terminal of the second switch is coupled to the power supply terminal and the second terminal of the second switch is coupled to the input of the second current source.

7. The device of claim 1, wherein the first input of the first transconductance amplifier is a non-inverting input, the second input of the transconductance amplifier is an inverting input, the first input of the amplifier is an inverting input, the second input of the amplifier is a non-inverting input, the first input of the second transconductance amplifier is a non-inverting input, and the second input of the second transconductance amplifier is an inverting input.

8. An apparatus comprising: Positive voltage power supply terminal; Negative voltage power supply terminal; A first transconductance amplifier having a first output and a second output; An amplifier having a first input, a second input, and an output, wherein the first input of the amplifier is coupled to the first output of a first transconductance amplifier, and the second input of the amplifier is coupled to the second output of the first transconductance amplifier; A resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the output of the amplifier; as well as A second transconductance amplifier has a first input, a second input, a first output, and a second output. The first input of the second transconductance amplifier is coupled to the second terminal of the resistor and the positive voltage power supply terminal. The second input of the second transconductance amplifier is coupled to the negative voltage power supply terminal. The first output of the second transconductance amplifier is coupled to the second output of the first transconductance amplifier and the second input of the amplifier. The second output of the second transconductance amplifier is coupled to the second output of the first transconductance amplifier and the second input of the amplifier.

9. The device of claim 8, wherein the resistor is a first resistor, the device further comprising: A second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first output of the first transconductance amplifier, the first input of the amplifier, and the second output of the second transconductance amplifier, and the second terminal of the second resistor being coupled to a common terminal; and A third resistor has a first terminal and a second terminal, the first terminal of the third resistor being coupled to the second output of the first transconductance amplifier, the second input of the amplifier and the first output of the second transconductance amplifier, and the second terminal of the third resistor being coupled to the common terminal.

10. The device of claim 8, wherein the first transconductance amplifier further has a first input and a second input, and the device further comprises: A digital-to-analog converter (DAC) having an input and an output, the output of the DAC being coupled to the first input of a first transconductance amplifier; and A processor having a first output and a second output, the first output of the processor being coupled to the input of the DAC, and the second output of the processor being coupled to the second input of the first transconductance amplifier.

11. The device of claim 8, wherein the resistor is a first resistor, and the second transconductance amplifier comprises: A first sensing amplifier has a first input, a second input, and an output, wherein the second input is the first input of the second transconductance amplifier; A first transistor has a first current terminal, a second current terminal, and a control terminal. The first current terminal of the first transistor is coupled to the second input of the first sense amplifier, the second current terminal of the first transistor is the second output of the second transconductance amplifier, and the control terminal of the first transistor is coupled to the output of the first sense amplifier. The second sensing amplifier has a first input, a second input, and an output, wherein the second input is the second input of the transconductance amplifier; The second transistor has a first current terminal, a second current terminal, and a control terminal. The first current terminal of the second transistor is coupled to the first input of the second sense amplifier, the second current terminal of the first transistor is the first output of the second transconductance amplifier, and the control terminal of the second transistor is coupled to the output of the second sense amplifier. as well as A second resistor has a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first current terminal of the first transistor and the first input of the first sensing amplifier, and the second terminal of the second resistor being coupled to the first current terminal of the second transistor and the first input of the second sensing amplifier.

12. The device of claim 11, wherein the second transconductance amplifier further comprises: A first current source having an output, the output of the first current source being coupled to a first current terminal of a first transistor, a first input of a first sense amplifier, and a first terminal of a second resistor; and A second current source having an output, the output of the second current source being coupled to the first current terminal of the second transistor, the first input of the second sense amplifier, and the second terminal of the second resistor.

13. The device of claim 12, wherein the first current source has an input, and the second current source has an input, and the second transconductance amplifier further comprises: A first switch having a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first switch is coupled to a power supply terminal, and the second terminal of the first switch is coupled to the input of the first current source; and The second switch has a first terminal, a second terminal, and a control terminal, wherein the first terminal of the second switch is coupled to the power supply terminal, and the second terminal of the second switch is coupled to the input of the second current source.

14. The device of claim 8, wherein the first input of the first transconductance amplifier is a non-inverting input, the second input of the transconductance amplifier is an inverting input, the first input of the amplifier is an inverting input, the second input of the amplifier is a non-inverting input, the first input of the second transconductance amplifier is a non-inverting input, and the second input of the second transconductance amplifier is an inverting input.

15. An apparatus comprising: A first switch having a first terminal and a second terminal; The second switch has a first terminal and a second terminal; The third switch has a first terminal and a second terminal; The fourth switch has a first terminal and a second terminal; A fifth switch has a first terminal and a second terminal, the second terminal being coupled to a common terminal; A first transconductance amplifier has a first output and a second output, the first output of the first transconductance amplifier being coupled to the second terminal of the first switch and the second terminal of the third switch, and the second output of the first transconductance amplifier being coupled to the second terminal of the second switch and the second terminal of the fourth switch; An amplifier having a first input, a second input, and an output, wherein the first input of the amplifier is coupled to the first output of a first transconductance amplifier, a second terminal of a first switch, and a second terminal of a third switch, and the second input of the amplifier is coupled to the second output of the first transconductance amplifier, a second terminal of a second switch, and a second terminal of a fourth switch; A resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the output of the amplifier; as well as A second transconductance amplifier has a first input, a second input, a first output, and a second output. The first input of the second transconductance amplifier is coupled to the second terminal of the resistor. The second input of the second transconductance amplifier is coupled to the output of the amplifier and the first terminal of the resistor. The first output of the second transconductance amplifier is coupled to the first terminal of the first switch. The second output of the second transconductance amplifier is coupled to the first terminal of the second switch. as well as A third transconductance amplifier has a first input, a second input, a first output, and a second output. The first input of the third transconductance amplifier is coupled to the second terminal of the resistor and the first input of the second transconductance amplifier. The second input of the third transconductance amplifier is coupled to the first terminal of the fifth switch. The first output of the third transconductance amplifier is coupled to the first terminal of the fourth switch. The second output of the third transconductance amplifier is coupled to the first terminal of the third switch.

16. The device of claim 15, wherein the amplifier is a current input amplifier.

17. The device of claim 15, wherein the first transconductance amplifier further has a first input and a second input, and the device further comprises: A digital-to-analog converter (DAC) having an input and an output, the output of the DAC being coupled to the first input of a first transconductance amplifier; and A processor having a first output and a second output, the first output of the processor being coupled to the input of the DAC, and the second output of the processor being coupled to the second input of the first transconductance amplifier.

18. The device of claim 15, wherein the resistor is a first resistor, and the second transconductance amplifier comprises: A first sensing amplifier has a first input, a second input, and an output, wherein the second input is the first input of the second transconductance amplifier; A first transistor has a first current terminal, a second current terminal, and a control terminal. The first current terminal of the first transistor is coupled to the second input of the first sensing amplifier, the second current terminal of the first transistor is the first output of the second transconductance amplifier, and the control terminal of the first transistor is coupled to the output of the first sensing amplifier. The second sensing amplifier has a first input, a second input, and an output, wherein the second input is the second input of the transconductance amplifier; The second transistor has a first current terminal, a second current terminal, and a control terminal. The first current terminal of the second transistor is coupled to the first input of the second sense amplifier, the second current terminal of the first transistor is the second output of the second transconductance amplifier, and the control terminal of the second transistor is coupled to the output of the second sense amplifier. as well as A second resistor has a first terminal and a second terminal, the first terminal of the second resistor being coupled to the first current terminal of the first transistor and the first input of the first sensing amplifier, and the second terminal of the second resistor being coupled to the first current terminal of the second transistor and the first input of the second sensing amplifier.

19. The device of claim 18, wherein the second transconductance amplifier further comprises: A first current source having an input and an output, the input of the first current source being coupled to a power supply terminal, and the output of the first current source being coupled to a first current terminal of a first transistor, a first input of a first sense amplifier, and a first terminal of a second resistor; and A second current source having an input and an output, the input of the second current source being coupled to the power supply terminal, and the output of the second current source being coupled to the first current terminal of the second transistor, the first input of the second sense amplifier, and the second terminal of the second resistor.

20. The device of claim 18, wherein the first input of the first transconductance amplifier is a non-inverting input, the second input of the transconductance amplifier is an inverting input, the first input of the amplifier is an inverting input, the second input of the amplifier is a non-inverting input, the first input of the second transconductance amplifier is a non-inverting input, the second input of the second transconductance amplifier is an inverting input, the first input of the third transconductance amplifier is a non-inverting input, and the second input of the third transconductance amplifier is an inverting input.

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