394 results about "Operational transconductance amplifier" patented technology

A chopper-stabilized amplifier receiving an input signal includes a first operational transconductance amplifier having an input chopper and an output chopper for chopping an output signal produced by the first operational transconductance amplifier. A switched capacitor notch filter filters the chopped output signal by operating synchronously with the chopping frequency of output chopper to filter ripple voltages that otherwise would be produced by the output chopper. In one embodiment, a second operational transconductance amplifier amplifies the notch filter output. The input signal is fed forward, summed with the output of the second operational transconductance amplifier, and applied to the input of a fourth operational transconductance amplifier. Ripple noise and offset are substantially reduced.

pH-change sensors and related methods are disclosed. One such sensor may have a first ion-sensitive transistor-operational-transconductance-amplifier (the “first IOTA”) and a second ion-sensitive transistor-operational-transconductance-amplifier (the “second IOTA”). Each IOTA may have an ion-sensitive transistor, a load transistor, and an output. In each IOTA, the drain region of the ion-sensitive transistor may be connected to the drain region of the load transistor. A differential sensor may be connected to the IOTAs, and an output from the differential sensor may indicate a voltage difference between the IOTA outputs. The output from the differential sensor may be used to provide an indication of a change in pH.

In low-voltage circuits, there is often insufficient voltage to use a current source to bias a transconductance amplifier stage. This is particularly true in mixers where a switching circuit must be stacked on top of the transconductance input stage. One way around this problem is to get "double-duty" out of the input differential pair, using it both for gain stage and for DC bias. This is done by AC coupling in a high-frequency input signal, while using a low-frequency, DC-coupled circuit to establish the proper bias level. One common technique is to use a simple current mirror scheme to establish the DC level. Proper biasing using this technique requires good matching of resistance. In some implementations of transconductance amplifiers, particularly those that use inductors as degeneration elements, series resistance of the inductor and interconnect resistance can cause significant errors in the bias current. This invention addresses that problem by using an operational amplifier with a current-sensing resistor and a low-frequency feedback loop to compensate automatically for any resistance errors. The operational amplifier drives the feedback voltage (generated in accordance with the sensed voltage at the current-sensing resistor and applied to one input of the operational amplifier) towards a reference voltage that is applied to the other input of the operational amplifier to bias the transistor(s) in the transconductance amplifier for desired operating conditions.

Circuits and methods to achieve dynamic biasing for the complete loop transfer function of a current mode voltage regulator have been achieved. The circuit comprises a Mirror-Transconductor Amplifier type operational transconductance amplifier (OTA) wherein its transconductance is linearly dependent on its biasing current. This biasing current is a linearly derivative of the OTA's output current. A current amplification circuit couples the regulator output current linearly with said OTA's output current. In this configuration the iterative biasing of the OTA forms a feed-forward loop, which contains a low-pass filter for stability and a negative feedback loop is closed by connecting the regulator voltage output to the OTA input. The invention realizes a purely current mode regulator since all internal currents are generated as a fraction of the output load.

According to one embodiment of the invention, a circuit comprising a plurality of operational transconductance amplifiers (OTAS) is described. The first OTA has differential input and differential output. The second OTA also has differential input, where a first output of the first OTA is coupled to the first differential input of the second OTA, which is an inverting input. A second output of the first OTA is coupled to the second input of the second OTA, which is a non-inverting input. The first differential output being coupled to a first input of the first OTA and the second differential output being coupled to a second input of the first OTA for negative feedback and current biasing.

A buck switching regulator includes a feedback control circuit including a first gain circuit generating a first feedback signal indicative of the regulated output voltage; a ripple generation circuit generating a ripple signal that is injected to the first feedback signal; and a comparator receiving a first reference signal and the first feedback signal to generate a comparator output signal. The switching regulator further includes an offset compensation circuit including a second gain circuit generating a second feedback signal indicative of the regulated output voltage; and an operational transconductance amplifier (OTA) configured to receive the second feedback signal and the first reference signal and to generate an output signal. The output signal of the OTA is coupled to the comparator to adjust an offset to the comparator so as to cancel the offset at the regulated output voltage due to the injected ripple signal.

Circuits and methods to achieve dynamic biasing for the complete loop transfer function of a current mode voltage regulator have been achieved. The circuit comprises a Mirror-Transconductor Amplifier type operational transconductance amplifier (OTA) wherein its transconductance is linearly dependent on its biasing current. This biasing current is a linearly derivative of the OTA's output current. A current amplification circuit couples the regulator output current linearly with said OTA's output current. In this configuration the iterative biasing of the OTA forms a feed-forward loop, which contains a low-pass filter for stability and a negative feedback loop is closed by connecting the regulator voltage output to the OTA input. The invention realizes a purely current mode regulator since all internal currents are generated as a fraction of the output load.

The invention discloses a low-power consumption broadband high-gain high-slew rate single-stage operational transconductance amplifier, which is formed by successively connecting a constant current bias stage, a differential input stage and a load current mirror transmission output stage in series. The load current mirror transmission output stage comprises eight N type MOS (metal oxide semiconductor) transistors from NM1 to NM8. Through the invention, the inherent limit restraint in a linear operational amplifying circuit is thoroughly solved, and the circuit performance under static AC small signals and dynamic big signals is comprehensively improved and enhanced.

A transconductance filter control system for compensating for drift in transconductance of a slave transconductance amplifier in a continuous time transconductance filter including: a master transconductance amplifier having an output which is a function of its transconductance and a control input for controlling the transconductance of the master transconductance amplifier; a tuning signal source for providing a tuning signal representative of a preselected characteristic of the transconductance filter; a comparing circuit, responsive to any deviation from a predetermined difference between the tuning signal and the output of the master transconductance amplifier, representative of a deviation of the transconductance of the master transconductance amplifier, for providing a compensation signal; and a circuit for applying the compensation signal to the control input of the master transconductance amplifier and to the control input of the slave transconductance amplifier in the transconductance filter to adjust the transconductance of both the master and slave transconductance amplifiers and restore the predetermined difference between the tuning signal and the output of the master transconductance amplifier.

An OTA capable of completely linear operation within the entire operable input range is provided. This OTA includes a differential pair of first and second bipolar transistors, a first current source / sink for driving the first transistor, a second current source / sink for driving the second transistor, and a resistor connected to an emitter of the first transistor and an emitter of the second transistor. The emitters of the first and second transistors are coupled together through the resistor. The differential pair has a pair of input terminals of the OTA. A first current mirror having an input terminal and an output terminal and a second current mirror having an input terminal and an output terminal are provided. The input terminal of the first current mirror is connected to the first transistor. The input terminal of the second current mirror is connected to the second transistor. The output terminal of the first current mirror and the output terminal of the second current mirror form a pair of output terminals of the OTA. An input signal to be amplified is differentially applied across the pair of input terminals of the OTA. An amplified output signal is differentially derived from the pair of output terminals of the OTA.

A chopper-stabilized amplifier receiving an input signal includes a first operational transconductance amplifier having an input chopper and an output chopper for chopping an output signal produced by the first operational transconductance amplifier. A switched capacitor notch filter filters the chopped output signal by operating synchronously with the chopping frequency of output chopper to filter ripple voltages that otherwise would be produced by the output chopper. In one embodiment, a second operational transconductance amplifier amplifies the notch filter output. The input signal is fed forward, summed with the output of the second operational transconductance amplifier, and applied to the input of a fourth operational transconductance amplifier. Ripple noise and offset are substantially reduced.

Disclosed are low power electronic devices configured to exploit the sub-threshold swing, unidirectional tunneling, and low-voltage operation of steep slope-tunnel tunnel field-effect transistors (TFET) to improve power-conversion efficiency and power-efficiency of electrical systems incorporating the TFET as an electrical component to perform energy harvesting, signal processing, and related operations. The devices include a HTFET-based rectifier having various topologies, a HTFET-based DC-DC charge pump converter, a HTFET-based amplifier having an amplifier circuit including a telescopic operational transconductance amplifier, and a HTFET-based SAR A / D converter having a HTFET-based transmission gate DFF. Any one of the devices may be used to generate a RF-powered system with improved power conversion efficiencies of power harvesters and power efficiencies of processing components within the system.

A bandgap reference system has a bandgap circuit, an operational transconductance amplifier, and an offset controller. The bandgap circuit includes a pair of diode devices and has a reference terminal at which is provided a bandgap reference voltage. The bandgap circuit provides a differential output having a first output and a second output. The operational transconductance amplifier has a first input coupled to the first output of the bandgap circuit, a second input coupled to the second output of the bandgap reference circuit, and an output coupled to the reference terminal. The offset controller is coupled to the operational transconductance amplifier and to the first and second outputs of the bandgap circuit. The offset controller trims the operational transconductance amplifier as needed to ensure an offset of the operational transconductance amplifier is below a predetermined level.

A linearization bias circuit for an RF BJT amplifier including a reference circuit, a current device and a transconductance amplifier. The linearization bias circuit controls the operating point of the BJT amplifier based on signal level of an input RF signal. The current device provides a constant reference current to the reference circuit, where the constant reference current has a level that is based on a desired collector current of the BJT amplifier. The reference circuit applies a predetermined relationship between DC and AC scale factors of collector current of the BJT amplifier. The transconductance amplifier asserts its output to maintain the constant reference current into the reference terminal of the reference circuit, and in doing so controls the base terminal of the BJT amplifier to modify its operating point to substantially maintain constant transconductance in the presence of varying input voltage amplitudes of the input RF signal.

The present invention discloses a bandgap reference circuit. The bandgap reference circuit includes an operational transconductance amplifier, and a reference generation circuit. The operational transconductance amplifier includes a self-biased operational transconductance amplifier, for utilizing an area difference between bipolar junction transistors of an input pair to generate a first positive temperature coefficient current to bias the input pair, and generating a positive temperature coefficient control voltage and a negative temperature coefficient control voltage; and a feedback voltage amplifier, for amplifying the negative temperature coefficient control voltage, and outputting a reference voltage to the input pair for feedback, to generate a first negative temperature coefficient current. The reference generation circuit generates a summation voltage or a summation current according to the positive temperature coefficient control voltage and the negative temperature coefficient control voltage.

The invention belongs to the technical field of power sources and relates to a self-adaptation voltage regulator circuit. The self-adaptation voltage regulator circuit comprises a power tube MP, a power tube MN, an inductor L, a capacitor C, a first resistor RF1, a second resistor RF2, a simulation phase lead compensation module, a delay phase lag compensation module, a critical path duplication module, a sawtooth wave generating module, a comparator and a power tube driver. The output voltage Vout is partitioned by the first resistor RF1 and the second resistor RF2. Simulation phase lead compensation is achieved through an operational amplifier, the resistor R1, the resistor R2 and the capacitor C. A load of an operational transconductance amplifier GM is RGM1 and provides the loop gain of APD compensation. The delay of the duplication of the critical path is compared with a system clock CLK through phase detection. Then, delay error signals are integrated through a charge pump. The output voltage VPD of the charge pump is connected to the positive going input end of the operational transconductance amplifier GM. PWM waveforms can be obtained by comparing the sawtooth wave current generated by an oscillator OSC and the output current of the GM. By means of the self-adaptation voltage regulator circuit, the power loss of a digital circuit is greatly reduced.

The invention discloses a low-noise passive frequency mixer. The low-noise passive frequency mixer comprises a low-noise transconductance amplifier stage, a switch frequency mixing stage and a transimpedance amplifier stage. The low-noise transconductance amplifier stage mainly adopts a cross coupling master-slave noise cancellation technology, a main transconductance conduit adopts a cross coupled structure to double an equivalent transconductance value, an appropriate transconductance value is provided through the main transconductance conduit and the noise of the main transconductance conduit is lowered through a master-slave structure; the switch frequency mixing stage is used for modulating and filtering radiofrequency currents output from the low-noise transconductance amplifier stage and outputting intermediate frequency currents; the transimpedance amplifier stage consists of a full-differential operational transconductance amplifier and a load resistor; the operational transconductance amplifier is based on a feed-forward compensation technology, and a consequent pole point in a transfer function of the amplifier is offset by a zero point introduced to a feed-forward stage of the operational transconductance amplifier, so that a large unity-gain bandwidth is achieved; the load resistor is used for converting the intermediate frequency currents into intermediate frequency voltage signals which are then output, by virtue of a voltage-current negative-feedback connection way. The low-noise passive frequency mixer has the characteristics of low noise, high gain and low power consumption.

An apparatus in an electronic device such as a buck converter circuit receives as a first input a voltage signal VSNS from the electronic device that represents a current through the electronic device, and receives as a second input a direct current reference voltage signal from a reference voltage source VREF. The apparatus regulates a direct current output IOUT of the electronic device with respect to the reference voltage source VREF by applying a pulse level transformation to the voltage signal VSNS using an operational transconductance amplifier.

A buck switching regulator includes a feedback control circuit including a first gain circuit configured to generate a first feedback signal indicative of the regulated output voltage; a ripple generation circuit configured to generate a ripple signal using the switching output voltage and to inject the ripple signal to the first feedback signal; a second gain circuit configured to generate a second feedback signal indicative of the regulated output voltage; an operational transconductance amplifier (OTA) configured to generate an output signal having a magnitude indicative the difference between the second feedback signal and the first reference signal; and a comparator configured to generate a comparator output signal having an output level indicative of the difference between the output signal of the OTA and the first feedback signal. As thus configured, the buck switching regulator generates an output voltage with increased accuracy and fast transient response.

A nested transimpedance amplifier (TIA) circuit comprises a zero-order TIA having an input and an output. A first transconductance amplifier has an input that communicates with said output of said zero-order TIA and an output. A first feedback resistance has one end that communicates with said input of said zero-order TIA and an opposite end that communicates with said output of said first transconductance amplifier. A first feedback capacitance has a first end that communicates with said input of said zero-order TIA and a second end that communicates with said output of said zero-order TIA. A capacitance has one end that communicates with said input of said zero-order TIA.

A DC-DC converter includes an error amplifier that includes an operational transconductance amplifier (OTA), a compensation circuit, and a fast transient controller. The OTA includes a compensation resistor, a compensation capacitor of Cz, and a Miller circuit. The equalization capacitance generated by the compensation capacitor and the Miller circuit is (1+k) Cz. The Miller circuit includes three transistors operated in the triode region. The ratio of the current through the transistors is 1:mk:(1−m)k. The current through the compensation capacitor in a second mode is (1+mk) times that in a first mode. The fast transient controller switches the Miller circuit between the first and second modes according to a feedback voltage dependent on the output voltage of the DC-DC converter.

Full-AC load flow constitutes a core computation in power system analysis. The present invention provides a performance gain with a hardware implementation of a sparse-linear solver using a Field Programmable Gate Array (FPGA). The invention also relates to the design, simulation, and hardware verification of a static transmission line model for analog power flow computation. Operational transconductance amplifiers are employed in the model based on a previously proposed DC emulation technique of power flow computation, and provide reconfigurability of transmission line parameters via transconductance gain. The invention also uses Analog Behavioral Models (ABMs) in an efficient strategy for designing analog emulation engines for large-scale power system computation. Results of PSpice simulations of these emulation circuits are compared with industrial grade numerical simulations for validation. The application is also concerned with the development of a generator model using analog circuits for load flow emulation for power system analysis to reduce computation time. The generator model includes reconfigurable parameters using operational transconductance amplifiers (OTAs). The circuit module is used with other reconfigurable circuits, i.e., transmission lines and loads.

Provided is a transconductor capable of eliminating a direct current (DC) offset component of a signal and compensating a mismatch of the signal. The transconductor includes amplifiers of simple circuit structures, and a common mode control DC offset elimination circuit. The transconductor includes a common mode control DC offset elimination circuit unit receiving input / output voltages to stabilize the current supplying and the output DC value, a first amplifier and a second amplifier reducing a mismatch in a transconductor circuit and increasing an output resistance, in order to prevent a signal distortion or a wrong operation of the circuit that is caused by the mismatch signal and unstable DC voltage.

A large-scale field-programmable analog array (FPAA) for rapidly prototyping analog systems and an arbitrary analog waveform generator. The large-scale FPAA includes a floating-gate transistor array and a plurality of computational analog blocks (CABs), which may be adapted to set bias voltages for operational transconductance amplifiers (OTAs), adjust corner frequencies on the capacitively coupled current conveyors, set multiplier coefficients in vector-matrix multipliers, and a variety of other operations. The floating-gate transistors may be used as switch elements, programmable resistor elements, precision current sources, and programmable transistors. Accordingly, the floating-gate transistors within the array allow on-chip programming of the characteristics of the computational elements, while still maintaining compact CABs. The arbitrary analog waveform generator may include programmable floating-gate MOS transistors for use as analog memory cells to store samples of the waveforms.

A programmable gain amplifier having three separately programmable amplifiers. A programmable transconductance amplifier is followed by a programmable transimpedance amplifier, then a programmable switched capacitor amplifier. In one embodiment, this programmable gain amplifier is implemented in an analog front-end (AFE) circuit. One AFE embodiment provides a coarse pre-gain offset a black reference level sampler, and a fine post-gain offset in the programmable switched capacitor amplifier. In one embodiment, an ADC reference is sampled, and is subtracted directly from the video signal in the switched capacitor amplifier so that the zero level of the video signal is made to correspond to the zero level of the ADC. In another embodiment, a piece-wise linear approximation of an exponential gain function is implemented by programming the transconductance and transimpedance amplifiers to provide exponential jumps in gain, while the switched capacitor amplifier is programmed to interpolate as needed between the exponential gain levels.

The invention discloses a gain increased operational transconductance amplifier which is formed in a manner that a bias constant current source is sequentially connected with differential input, a load current mirror, a cascode output stage and an adjustable auxiliary differential pair in sequence, wherein the differential input is composed of four PMOS pipes namely M1a, M2a, M1b and M2b; the load current mirror is composed of six NMOS pipes namely M3, M4, M5a, M6a, M5b and M6b; the cascode output stage is composed of six MOS pipes namely M7, M8, M9, M10, M11 and M12; the adjustable auxiliary differential pair is composed of M13, M14 and M15. Reutilization of current and the output stage increased adjustable auxiliary differential pair thoroughly solve the inherent contradiction among gain, bandwidth, power dissipation and the like in a circuit; the gain increased operational transconductance amplifier is slightly influenced by output voltage, an additional pole is not introduced, the simulation results show same static power dissipation, and multiplication is realized for gain and bandwidth; the gain increased operational transconductance amplifier further has the characteristics of fine tuning and high accuracy and is applicable to communication, electronic measurement and automatic control systems.

A buck switching regulator includes a feedback control circuit including a feedback network including first and second gain circuits configured to generate first and second feedback signals, respectively, indicative of the regulated output voltage; a ripple generation circuit configured to inject a ripple signal to the first gain circuit; an operational transconductance amplifier (OTA) configured to receive the second feedback signal and a reference signal and to generate an output signal being coupled to the first gain circuit to adjust the first feedback signal; and a comparator configured to receive the first feedback signal and the reference signal and to generate a comparator output signal. The output signal of the OTA is applied to the first feedback signal to cancel a voltage offset in the regulated output voltage due to the injected ripple signal to the first gain circuit.