Non-linear compensation in bandpass filters

Abstract

Methods, apparatus, systems, and articles of manufacture corresponding to current limiting circuitry with controlled current variation are described. An example circuit (250, 350, 450, 550, 650, 750, 850, 950, 105) includes an amplifier (204, 404) having an input terminal and an output terminal; a capacitor (210) having a first terminal and a second terminal, the first terminal of the capacitor (210) being coupled to the input terminal of the amplifier (204, 404), the second terminal of the capacitor (210) being coupled to the output terminal of the amplifier (204, 404); and a diode circuitry (214, 555, 855) having a first terminal and a second terminal, the first terminal of the diode circuitry (214, 555, 855) being coupled to the first terminal of the capacitor (210) and the input terminal of the amplifier (204, 404), the second terminal of the diode circuitry (214, 555, 855) being coupled to the second terminal of the capacitor (210) and the output terminal of the amplifier (204, 404).

Description

Technical Field

[0001] The present disclosure relates generally to circuits and, more particularly, to bandpass filters with nonlinear compensation. Background Art

[0002] Bandpass filters are electrical components that block low-frequency and high-frequency signals and allow signals within a certain frequency range to pass. Bandpass filters are used in a wide range of fields, including medical imaging, telecommunications, data transmission, and / or other fields that utilize analog signals. In some examples, the bandpass filter is implemented by a feedback system including two back-to-back integrators. The integrator can be implemented by an amplifier (e.g., a differential amplifier, a fully differential amplifier, etc.) in combination with other components (e.g., resistors, capacitors, etc.). Summary of the invention

[0003] In at least one example of the specification, a circuit includes an amplifier having an input terminal and an output terminal; a capacitor having a first terminal and a second terminal, the first terminal of the capacitor being coupled to the input terminal of the amplifier, and the second terminal of the capacitor being coupled to the output terminal of the amplifier; and a diode circuit system having a first terminal and a second terminal, the first terminal of the diode circuit system being coupled to the first terminal of the capacitor and the input terminal of the amplifier, and the second terminal of the diode circuit system being coupled to the second terminal of the capacitor and the output terminal of the amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 An example medical imaging machine for implementing a bandpass filter in conjunction with the examples described herein is provided.

[0005] Figure 2 for Figure 1 An example fully differential implementation of a bandpass filter.

[0006] Figure 3 for Figure 2 An example fully differential circuit implementation of a bandpass filter.

[0007] Figure 4 for Figure 1 An example differential implementation of a bandpass filter.

[0008] Figure 5 for Figure 1 An example alternative fully differential implementation of a bandpass filter.

[0009] Figure 6 for Figure 5 An example fully differential circuit implementation of a bandpass filter.

[0010] Figure 7 for Figure 1 An example alternative differential implementation of a bandpass filter.

[0011] Figure 8 for Figure 1 An example alternative fully differential implementation of a bandpass filter.

[0012] Fig. 9 for Figure 8 An example fully differential circuit implementation of a bandpass filter.

[0013] Fig.10 for Figure 1 An example alternative differential implementation of a bandpass filter.

[0014] Fig.11 For Figure 1 , 2 , 3, 4, 5, 6, 7, 8, 9 and / or 10, a flowchart representation of the methods and / or operations performed by the bandpass filters.

[0015] Fig.12 is an example timing diagram described in conjunction with the examples described herein.

[0016] The same reference numbers or other reference numerals are used in the drawings to indicate the same or similar (functional and / or structural) features. DETAILED DESCRIPTION

[0017] The drawings are not necessarily drawn to scale. Generally, the same reference numerals in the drawings and the specification refer to the same or similar parts. Although the drawings show regions with clear lines and boundaries, some or all of these lines and / or boundaries may be idealized. In practice, boundaries and / or lines may be unobservable, mixed, and / or irregular.

[0018] Some bandpass filters utilize a feedback system with two back-to-back integrators. A bandpass filter allows signals to pass within a frequency range defined by a center frequency and a bandwidth. The center frequency (referred to herein as ω0) is the frequency at which the bandpass filter gain is the set passband gain. The bandwidth (BW or ω B ) corresponds to the frequency range above and below the center frequency through which the signal can pass with less than X (e.g., 3) db of attenuation, e.g., the lowest and highest frequencies corresponding to a threshold gain amount below the center frequency gain. The bandwidth of a bandpass filter is characterized by a quality value (Q). The quality value or quality factor of a bandpass filter is the center frequency divided by the bandwidth (Q = ω0 / ω B ). For a given center frequency, higher quality values ​​correspond to narrower passbands and lower quality corresponds to wider passbands.

[0019] As described above, the bandpass filter may include two back-to-back integrators. For example, a Tow-Thomas biquad bandpass filter includes two back-to-back integrators. In order to control the characteristics of the bandpass filter (e.g., center frequency and / or bandwidth), the bandpass filter may be implemented using a lossy integrator (also called a practical integrator) and a lossless integrator. The lossless integrator includes an amplifier having one input terminal coupled to an output terminal via a capacitor and does not include a feedback resistor. The lossy integrator includes an amplifier having one input terminal coupled to an output terminal via a capacitor and a resistor (e.g., a feedback resistor) in parallel. Both types of integrators include a resistor (e.g., an input resistor) coupled to the input of the amplifier. The transfer function of the lossy integrator is Where R1 is the input resistor, R2 is the feedback resistor, C is the capacitor, and s is a complex variable corresponding to the relationship between the output and the input of the lossy input system. Because the transfer function of the lossy integrator corresponds to the resistance of the resistor, a resistor with a specific resistance can be selected to control the center frequency and / or bandwidth of the bandpass filter. For example, the quality and / or bandwidth of the bandpass filter is based on the selected resistance of the feedback resistor.

[0020] As mentioned above, the bandpass filter includes a feedback loop. Therefore, if the design is not appropriate, the bandpass filter may be unstable. The bandpass filter may also exhibit signal-dependent stability behavior. Therefore, simple small signal stability is not sufficient to ensure the stability of the filter over the entire operating voltage swing range. If the amplitude of the input signal is too high, for example due to noise and / or characteristics of the device generating the input signal, then the instability of the bandpass filter leads to continuous oscillations at the output of the bandpass filter. The stability of the bandpass filter depends on the frequency of the non-dominant poles of the bandpass filter and the frequency of the unity gain crossover point of the bandpass back-to-back integrator loop. The non-dominant poles of the bandpass filter are located at a frequency corresponding to the ratio of the center frequency and the quality factor (e.g., ω c / Q). The unity gain crossover point (also called unity gain crossover) is the frequency at which the gain of the lossy integrator is 0 dB. The phase loss contribution of the non-dominant pole of the post loop at the unity gain crossover point reduces the phase margin of the loop, thereby reducing the stability of the bandpass filter. For example, the closer the frequency of the non-dominant pole is to the unity gain crossover point, the greater the impact of the phase of the non-dominant pole on the phase margin of the unity gain crossover point, which corresponds to a less stable system.

[0021] The examples described herein increase the stability of the bandpass filter by reducing the feedback resistance of the lossy integrator in response to the input voltage exceeding a first threshold or falling below a second threshold. The DC gain of the lossy amplifier is a function of the feedback resistance (e.g., -R2 / R1). The DC gain corresponds to the quality factor (Q) of the filter and determines the unity gain crossing of the feedback loop. In addition, as described above, the frequency of the non-dominant pole is a function of the quality of the lossy integrator, and the quality of the lossy integrator is a function of the feedback resistance. Therefore, by reducing the feedback resistance in response to the input voltage exceeding the maximum threshold (or falling below the minimum threshold), the frequency of the unity gain crossing point is reduced to a lower frequency, and the frequency of the non-dominant pole is increased at a frequency that increases the distance between the two frequencies. Therefore, the phase contribution of the non-dominant pole has a small (or zero) effect on the phase margin of the unity gain crossing point, thereby increasing the stability of the bandpass filter. The examples described herein utilize a diode circuit system as feedback in a lossy integrator to reduce the feedback resistance of the lossy integrator in response to the input voltage exceeding a threshold, as described further below. The examples described herein produce a stable system that is reliable and provides fast overload recovery in a bandpass filter.

[0022] Figure 1 An example image scanner 100 is described. Figure 1 The image scanner 100 includes an example image capture component 102, an example front-end amplification state circuit system 104, an example bandpass filter 106 (also referred to as a bandpass filter circuit or bandpass filter circuit system), an example analog-to-digital converter (ADC) 108, and an example image processing circuit system 110. Although the bandpass filter 106 is Figure 1 , but the bandpass filter 106 may be implemented by itself (e.g., in a dedicated circuit or IC) or in any circuit in which a bandpass filter is desired, such as audio processing, image processing, telecommunications, automotive systems, and / or any other type of electronic device that may include a bandpass filter. Figure 1 The image scanner 100 is a medical image scanner, such as a magnetic resonance imaging (MRI) machine, an ultrasound machine, etc. However, the image scanner 100 may be any type of image scanner. Although the example components are connected via two connections (e.g., an inverting connection and a non-inverting connection), the components may be connected via a single connection. The non-inverting connection corresponds to an analog signal generated by the image capture component 102. The analog signal is referred to herein as a non-inverting input signal. The inverting connection corresponds to the inversion of the analog signal generated by the image capture component 102. The inversion of the analog signal is referred to herein as an inverting input signal.

[0023] The image capture component 102 is a sensor and / or transducer that transmits and / or receives signals to generate an image. For example, in an ultrasound system, the image capture component 102 transmits sound waves into the body. The image capture component 102 then receives or senses the reflected sound waves reflected from the body tissue. In an MRI system, the image capture component 102 generates a magnetic field and detects the energy released when protons realign with the magnetic field. The image capture component 102 transmits one or more analog signals corresponding to the image to the front-end amplifier state circuit system 104. The front-end amplifier state circuit system 104 is an instrumentation amplifier topology that amplifies the signal from the image capture component 102. The front-end amplifier state circuit system 104 outputs the amplified image signal to the bandpass filter 106.

[0024] Figure 1 The bandpass filter 106 filters out high frequency signals (e.g., signals above a first frequency threshold) and low frequency signals (e.g., signals below a second frequency threshold). As further described below, the bandpass filter 106 reduces feedback resistance in response to the input signal exceeding a maximum threshold amplitude (or falling below a minimum threshold amplitude), thereby reducing the frequency of the unity gain crossover point and increasing the frequency of the non-dominant pole. The difference between the frequencies of the unity gain crossover point and the non-dominant pole increases, so that the phase contribution of the non-dominant pole has a smaller impact on the phase margin of the unity gain crossover point. As described above, reducing the impact of the phase contribution of the non-dominant pole on the phase margin of the unity gain crossover point increases the stability of the bandpass filter 106. The bandpass filter 106 outputs the filtered output to the ADC 108. The ADC 108 converts the filtered analog signal into a digital value, which the image processing circuit system 110 uses to generate an image that can be output by an interface (e.g., a user interface). The following is combined with Figure 2-10 The bandpass filter 106 is further described.

[0025] Figure 2 For the realization of Figure 1 An example circuit diagram of an example bandpass filter 250 of the bandpass filter 106 is shown. Figure 2 The bandpass filter 250 includes an example lossy integrator 200 and an example lossless integrator 202. As described above, the lossy integrator includes a feedback resistor coupled in parallel to a feedback capacitor. However, the lossless integrator only includes a feedback capacitor. The lossy integrator 200 includes an example fully differential amplifier 204, example resistors 206, 208, example feedback capacitors 210, 212, example diode circuitry 214, 222, example diodes 216, 220, 224, 228, and example resistors 218, 226. The example bandpass filter 250 additionally includes feedback resistors 230, 232. The fully differential amplifier 204 has a differential input and a differential output.

[0026] The output of the example front end amplification state circuitry 104 is coupled to the input terminal of the lossy integrator 200. The output terminal of the lossy integrator 200 is coupled to the input terminal of the lossless integrator 202. The output terminal of the lossless integrator 202 is coupled to the input terminal of the fully differential amplifier 204 via feedback resistors 230, 232.

[0027] Figure 2 The fully differential amplifier 204 amplifies the input signal. The fully differential amplifier 204 has two input terminals (e.g., an inverting input terminal and a non-inverting input terminal) and two output terminals (e.g., an inverting output terminal and a non-inverting output terminal). The first input terminal (e.g., the inverting input terminal) of the fully differential amplifier 204 is coupled to the second terminal of the resistor 206, the first terminal of the resistor 230, the cathode terminal of the diode 216, the first terminal of the resistor 218, the anode terminal of the diode 220, and the first terminal of the capacitor 210. The second input terminal (e.g., the non-inverting input terminal) of the fully differential amplifier 204 is coupled to the first terminal of the resistor 232, the cathode terminal of the diode 224, the first terminal of the resistor 226, the anode terminal of the diode 228, and the first terminal of the capacitor 212. A first output terminal (e.g., a non-inverting output terminal) of fully differential amplifier 204 is coupled to ADC 108, a first input terminal of lossless integrator 202, an anode terminal of diode 216, a second terminal of resistor 218, a cathode terminal of diode 220, and a second terminal of capacitor 210. A second output terminal (e.g., an inverting output terminal) of fully differential amplifier 204 is coupled to ADC 108, a second input terminal of lossless integrator 202, an anode terminal of diode 224, a second terminal of resistor 226, a cathode terminal of diode 228, and a second terminal of capacitor 212.

[0028] Figure 2The input resistors 206, 208 of the lossy integrator 200 have two terminals. The first terminals of the resistors 206, 208 are coupled to the front-end amplification state circuit system 104. The second terminal of the resistor 206 is coupled to the first terminal of the resistor 230, the cathode terminal of the diode 216, the first terminal of the resistor 218, the anode terminal of the diode 220, the first terminal of the capacitor 210, and the first input terminal of the fully differential amplifier 204. The second terminal of the resistor 208 is coupled to the first terminal of the resistor 232, the cathode terminal of the diode 224, the first terminal of the resistor 226, the anode terminal of the diode 228, the first terminal of the capacitor 212, and the second input terminal of the fully differential amplifier 204. The resistance of the resistors 206, 208 can be selected based on the desired gain of the lossy amplifier 200. The non-inverting input signal from the front-end amplification state circuit system 104 is received via the resistor 206, and the inverting input signal of the front-end amplification state circuit system 104 is received via the resistor 208. The resistance of resistors 206 , 208 may be selected for a desired quality value (Q) and / or a desired passband gain (Av).

[0029] Figure 2 The feedback capacitors 210, 212 of the amplifier 204 are short-circuited to high frequency signals and bypass the resistance of the corresponding resistors 218, 226 and / or the resistance of the corresponding diodes 216, 220, 224, 228. The resistance of the resistors 218, 226 can be selected for a desired quality value (Q). In addition, the capacitors 210, 212 reduce the gain of the amplifier 204. The first terminal of the capacitor 210 is coupled to the first terminal of the resistor 230, the cathode terminal of the diode 216, the first terminal of the resistor 218, the anode terminal of the diode 220, the second terminal of the resistor 206, the first terminal of the resistor 230, and the first input terminal of the fully differential amplifier 204.

[0030] Figure 2 The diode circuit system 214, 222 reduces the feedback resistance of the fully differential amplifier 204 in response to the input voltage exceeding the first threshold or falling below the second threshold. Figure 2 In FIG. 1 , diode circuit system 214 includes diodes 216, 220 and resistor 218. In addition, diode circuit system 222 includes diodes 224, 228 and resistor 226. However, diode circuit system 214 may be implemented using transistors, as shown below in combination with Figure 5-10 Also described.

[0031] Figure 2The diode 216 has an anode terminal and a cathode terminal. The anode terminal of the diode 216 is coupled to the second terminal of the resistor 218, the cathode terminal of the diode 220, the second terminal of the capacitor 210, the first output terminal of the fully differential amplifier 204, the ADC 108, and the first input of the lossless integrator 202. The cathode terminal of the diode 216 is coupled to the first terminal of the resistor 218, the anode terminal of the diode 220, the first terminal of the capacitor 210, the second terminal of the resistor 206, the first terminal of the resistor 230, and the first input terminal of the fully differential amplifier 204. The diode 216 operates as a high (e.g., infinite) resistance resistor in response to the output voltage dropping below a threshold voltage (e.g., the conduction, forward voltage, and / or nonlinear compensation voltage of the diode 216), and operates as a low resistance (also referred to as low impedance) closed switch in response to the output voltage exceeding the threshold voltage.

[0032] Figure 2 Resistor 218 is a feedback resistor that is selected for specific characteristics of lossy integrator 200, such as bandwidth, gain, center frequency, and / or quality. Resistor 218 has two terminals. A first terminal of resistor 218 is coupled to a cathode terminal of diode 216, an anode terminal of diode 220, a first terminal of capacitor 210, a second terminal of resistor 206, a first terminal of resistor 230, and a first terminal of fully differential amplifier 204. A second terminal of resistor 218 is coupled to an anode terminal of diode 216, a cathode terminal of diode 220, a second terminal of capacitor 210, a first output terminal of fully differential amplifier 204, ADC 108, and a first output of lossless integrator 202.

[0033] Figure 2 The diode 220 includes an anode terminal and a cathode terminal. The cathode terminal of the diode 220 is coupled to the second terminal of the resistor 218, the anode terminal of the diode 216, the second terminal of the capacitor 210, the first output terminal of the fully differential amplifier 204, the ADC 108, and the first input lossless integrator 202. The cathode terminal of the diode 220 is coupled to the first terminal of the resistor 218, the anode terminal of the diode 216, the first terminal of the capacitor 210, the second terminal of the resistor 206, the first terminal of the resistor 230, and the first input terminal of the fully differential amplifier 204. The diode 220 operates as a high (e.g., infinite) resistance resistor in response to the output voltage dropping below a threshold voltage, e.g., the conduction or forward voltage of the diode 220. In addition, the diode 220 operates as a low resistance closed switch in response to the output voltage exceeding the threshold voltage.

[0034] Figure 2The diode 224 includes an anode terminal and a cathode terminal. The anode terminal of the diode 224 is coupled to the second terminal of the resistor 226, the cathode terminal of the diode 228, the second terminal of the capacitor 210, the second output terminal of the fully differential amplifier 204, the ADC 108, and the first input lossless integrator 202. The cathode terminal of the diode 224 is coupled to the first terminal of the resistor 226, the anode terminal of the diode 228, the first terminal of the capacitor 210, the second terminal of the resistor 208, the first terminal of the resistor 232, and the second input terminal of the fully differential amplifier 204. The diode 224 operates as a high (e.g., infinite) resistance resistor in response to the output voltage dropping below a threshold voltage (e.g., the conduction or forward voltage of the diode 224), and operates as a low resistance closed switch in response to the output voltage exceeding the threshold voltage.

[0035] Figure 2 Resistor 226 is a feedback resistor that is selected for specific characteristics of lossy integrator 200, such as bandwidth, gain, center frequency, and / or quality. Resistor 226 has two terminals. A first terminal of resistor 226 is coupled to a cathode terminal of diode 224, an anode terminal of diode 228, a first terminal of capacitor 210, a second terminal of resistor 208, a first terminal of resistor 232, and a second input terminal of fully differential amplifier 204. A second terminal of resistor 226 is coupled to an anode terminal of diode 224, a cathode terminal of diode 228, a second terminal of capacitor 210, a second output terminal of fully differential amplifier 204, ADC 108, and a first input of lossless integrator 202.

[0036] Figure 2 The diode 228 has an anode terminal and a cathode terminal. The cathode terminal of the diode 228 is coupled to the second terminal of the resistor 226, the anode terminal of the diode 224, the second terminal of the capacitor 210, the second output terminal of the fully differential amplifier 204, the ADC 108, and the first input lossless integrator 202. The cathode terminal of the diode 228 is coupled to the first terminal of the resistor 226, the anode terminal of the diode 224, the first terminal of the capacitor 210, the second terminal of the resistor 208, the first terminal of the resistor 232, and the second input terminal of the fully differential amplifier 204. The diode 228 operates as a high (e.g., infinite) resistance resistor in response to the output voltage falling below a threshold voltage (e.g., the conduction or forward voltage of the diode 228), and operates as a low resistance closed switch in response to the output voltage exceeding the threshold voltage.

[0037] In operation, in response to the non-inverting input voltage being above a first threshold voltage (e.g., -0.7 volts (V)) and below a second threshold voltage (e.g., 0.7 V), the diodes 216, 220 are turned off, causing the diodes 216, 220 to operate as an open circuit. Thus, the resistance between the first input terminal of the fully differential amplifier 204 and the first output terminal of the fully differential amplifier 204 is a function of the resistance of the resistor 218. In this manner, the gain of the lossy integrator 200, the frequency of the unity gain crossover point, and the frequency of the non-dominant pole are operated based on the resistance of the example resistor 218.

[0038] However, in response to the non-inverting input voltage exceeding the second threshold voltage, the diode 220 is turned on, allowing current to flow through the diode 220 and capping the output voltage to prevent the output voltage from exceeding the second threshold voltage. When the diode 220 is turned on, the diode 220 has a small amount of resistance (e.g., about 50 ohms). Therefore, the resistance between the first input terminal of the fully differential amplifier 204 and the first output terminal of the fully differential amplifier 204 is significantly reduced. For example, the resistance of the diode 220 is now connected in parallel with the resistor 218, thereby reducing the overall feedback resistance. Reducing the feedback resistance reduces the gain of the fully differential amplifier 204, reduces the frequency of the unity gain crossover point, and increases the frequency of the non-dominant pole. Therefore, reducing the feedback resistance increases the frequency between the unity gain crossover point and the non-dominant pole to increase the stability of the bandpass filter 250.

[0039] In addition, in response to the non-inverting input voltage falling below the first threshold voltage, diode 216 turns on, allowing current to flow through diode 216 and capping the output voltage to prevent the output voltage from falling below the first threshold voltage. Because diode 216 has a small amount of resistance (e.g., about 50 ohms), the resistance between the first input terminal of the fully differential amplifier 204 and the first output terminal of the fully differential amplifier 204 is significantly reduced because the resistance of diode 216 is now connected in parallel with resistor 218, thereby reducing the overall feedback resistance. Reducing the feedback resistance reduces the gain of the fully differential amplifier 204, reduces the frequency of the unity gain crossover point, and increases the frequency of the non-dominant pole. Therefore, reducing the feedback resistance increases the frequency between the unity gain crossover point and the non-dominant pole to increase the stability of the bandpass filter 250. The diode circuit system 222 operates in the same manner to reduce the gain of the fully differential amplifier 204 and move the frequency of the non-dominant pole and the unity gain crossover point based on the inverting input signal. Furthermore, to achieve symmetry of the inverting and non-inverting input signals, the resistance of resistor 226 may be the same as the resistance of resistor 218. However, the resistances of resistors 218, 226 may be any resistance.

[0040] Figure 3 A circuit implementation for using the lossless integrator 202 is described to implement Figure 2 An example bandpass filter 350 of the example bandpass filter 106 . Figure 3 The bandpass filter 350 includes Figure 2 An example lossy integrator 200 and an example lossless integrator 202 are shown. Figure 3 The lossy integrator 200 includes Figure 2 An example fully differential amplifier 204 , example resistors 206 , 208 , example feedback capacitors 210 , 212 , example diode circuitry 214 , 222 , example diodes 216 , 220 , 224 , 228 , and example resistors 218 , 226 . Figure 3 The example bandpass filter 350 additionally includes Figure 2 The example lossless integrator 202 includes example resistors 300 , 302 , an example fully differential amplifier 304 , and example capacitors 306 , 308 .

[0041] Lossless Integrator 202 Figure 3 Resistors 300, 302 are input resistors that receive the output of the fully differential amplifier 204. A first terminal of resistor 300 is coupled to an anode terminal of diode 216, a second terminal of resistor 218, a cathode terminal of diode 220, a second terminal of capacitor 210, a first output terminal of the fully differential amplifier 204, and ADC 108. A second terminal of resistor 300 is coupled to a first terminal of capacitor 306 and a first input terminal of the fully differential amplifier 304. A first terminal of resistor 302 is coupled to an anode terminal of diode 224, a second terminal of resistor 226, a cathode terminal of diode 228, a second terminal of capacitor 212, a second output terminal of the fully differential amplifier 204, and ADC 108. A second terminal of resistor 302 is coupled to a first terminal of capacitor 308 and a second input terminal of the fully differential amplifier 304. The resistances of resistors 300, 302 may be selected for a desired gain of the lossless integrator 202.

[0042] Figure 3The fully differential amplifier 304 amplifies the output signal of the fully differential amplifier 204. The output of the fully differential amplifier 304 is fed back to the input of the fully differential amplifier 204 via the corresponding resistors 230, 232. The fully differential amplifier 304 has two input terminals and two output terminals. The first input terminal of the fully differential amplifier 304 is coupled to the second terminal of the resistor 300 and the first terminal of the capacitor 306. The second input terminal of the fully differential amplifier 304 is coupled to the second terminal of the resistor 302 and the first terminal of the capacitor 308. The first output terminal of the fully differential amplifier 304 is coupled to the second terminal of the capacitor 306 and the second terminal of the resistor 230. The second output terminal of the fully differential amplifier 304 is coupled to the second terminal of the capacitor 308 and the second terminal of the resistor 232.

[0043] Figure 2 Capacitors 306 and 308 are feedback capacitors. The gain of amplifier 204 is a function of the capacitance of capacitors 306 and 308. A first terminal of capacitor 306 is coupled to a second terminal of resistor 300 and a first input terminal of fully differential amplifier 304. A second terminal of capacitor 306 is coupled to a first output terminal of fully differential amplifier 304 and a second terminal of resistor 230. A first terminal of capacitor 308 is coupled to a second terminal of resistor 302 and a second input terminal of fully differential amplifier 304. A second terminal of capacitor 308 is coupled to a second output terminal of fully differential amplifier 304 and a second terminal of resistor 232.

[0044] Figure 4 Description for implementation Figure 1 An example bandpass filter 450 of example bandpass filter 106 has a "standard" differential amplifier with a differential input and a single-ended output. Figure 4 The bandpass filter 450 includes the example lossy integrator 400 and the example lossless integrator 402 . Figure 4 The lossy integrator 400 includes Figure 2 and / or 3's resistors 206 , 218 , diode circuitry 214 , diodes 216 , 220 , and capacitor 210 . Figure 4 The lossy integrator 400 further includes a differential amplifier 404 . Figure 4 The lossless integrator 402 includes Figure 3 The lossless integrator 402 further includes an example differential amplifier 406 and an example inverter 408. Figure 4 The bandpass filter 450 additionally includes Figure 2 and / or a feedback resistor 230 of 3.

[0045] exist Figure 4In the example lossy integrator 400, resistors 206, 218, capacitor 210, diode circuitry 214, and diodes 216, 220 are connected to Figure 2 3. However, in the lossy integrator 400, the fully differential amplifier 204 is replaced by a differential amplifier 404 (e.g., an operational amplifier, an error amplifier, etc.) and receives only one input signal. The differential amplifier 404 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminal of the differential amplifier 404 is coupled to the second terminal of the resistor 206, the first terminal of the resistor 230, the cathode terminal of the diode 216, the first terminal of the resistor 218, the anode terminal of the diode 220, and the first terminal of the capacitor 210. The non-inverting input terminal of the differential amplifier 404 is coupled to the ground. The output terminal of the differential amplifier 404 is coupled to the ADC 108, the first input terminal of the lossless integrator 202, the anode terminal of the diode 216, the second terminal of the resistor 218, the cathode terminal of the diode 220, and the second terminal of the capacitor 210.

[0046] exist Figure 4 In the example lossless integrator 402, the resistor 300 and the capacitor 306 are connected with Figure 3 4. However, in the lossless integrator 402, the fully differential amplifier 304 is replaced by a differential amplifier 406. The differential amplifier 406 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminal of the differential amplifier 406 is coupled to the second terminal of the resistor 300 and the first terminal of the capacitor 306. The non-inverting input terminal of the differential amplifier 406 is coupled to the ground. The output terminal of the differential amplifier 406 is coupled to the second terminal of the capacitor 306 and the input terminal of the inverter 408.

[0047] Figure 4 The inverter 408 inverts the output of the amplifier 406. The inverter 408 has an input terminal and an output terminal. The input terminal of the inverter 408 is coupled to the second terminal of the capacitor 306 and the output terminal of the amplifier 406. The output terminal of the inverter 408 is coupled to the resistor 230.

[0048] Figure 5 Description for implementation Figure 1 Example bandpass filter 550 of example bandpass filter 106 . Figure 5 The bandpass filter 550 includes Figure 2 500 and the example lossless integrator 202. Figure 5 The lossy integrator 500 includes Figure 2 An example fully differential amplifier 204 , example resistors 206 , 208 , and example feedback capacitors 210 , 212 . Figure 5The example bandpass filter 550 additionally includes Figure 2 The feedback resistors 230, 232 are connected to the Figure 5 In the example diode circuitry 555, 560 are replaced with the example resistors 501, 502, 504, 506, 512, 514, 516, 518 and the example transistors 508, 510, 520, 522 Figure 2-4 Diodes 216 , 220 , 224 , 228 and resistors 218 , 226 .

[0049] Figure 5 Resistors 501, 502, 504, 506 each have two terminals. A first terminal of resistor 501 is coupled to a first current terminal of transistor 508, a first terminal of resistor 504, a first current terminal of transistor 510, a first terminal of capacitor 210, a first terminal of resistor 230, a second terminal of resistor 206, and a first input terminal of fully differential amplifier 204. A second terminal of resistor 501 is coupled to a first terminal of resistor 502 and a control terminal of transistor 508. A first terminal of resistor 502 is coupled to a second terminal of resistor 501 and a control terminal of transistor 508. A second terminal of resistor 502 is coupled to a second current terminal of transistor 508, a second terminal of resistor 506, a second current terminal of transistor 510, a second terminal of capacitor 210, a first output terminal of fully differential amplifier 204, ADC 108, and a first input terminal of lossless integrator 202. A first terminal of resistor 504 is coupled to a first current terminal of transistor 508, a first terminal of resistor 501, a first current terminal of transistor 510, a first terminal of capacitor 210, a first terminal of resistor 230, a second terminal of resistor 206, and a first input terminal of fully differential amplifier 204. A second terminal of resistor 504 is coupled to a first terminal of resistor 506 and a control terminal of transistor 510. A first terminal of resistor 502 is coupled to a second terminal of resistor 504 and a control terminal of transistor 510. A second terminal of resistor 502 is coupled to a second current terminal of transistor 508, a second terminal of resistor 502, a second current terminal of transistor 510, a second terminal of capacitor 210, a first output terminal of fully differential amplifier 204, ADC 108, and a first input terminal of lossless integrator 202.

[0050] Figure 5The transistors 508, 510 are bipolar junction transistors (BJT). However, the transistors 508, 510 may be metal oxide semiconductor field effect transistors (MOSFET) and / or any other type of transistor. The transistors 508, 510 each have two "current" terminals (e.g., an emitter terminal and a collector terminal) and a control terminal (e.g., a base terminal). The first current terminal of the transistor 508 is coupled to the terminal of the resistor 501, the first terminal of the resistor 504, the first current terminal of the transistor 510, the first terminal of the capacitor 210, the first terminal of the resistor 230, the second terminal of the resistor 206, and the first input terminal of the fully differential amplifier 204. The second current terminal of the transistor 508 is coupled to the second terminal of the resistor 502, the second terminal of the resistor 506, the second current terminal of the transistor 510, the second terminal of the capacitor 210, the first output terminal of the fully differential amplifier 204, the ADC 108, and the first input terminal of the lossless integrator 202. A control terminal of transistor 508 is coupled to a second terminal of resistor 501 and a first terminal of resistor 502. A first current terminal of transistor 510 is coupled to a terminal of resistor 501, a first terminal of resistor 504, a first current terminal of transistor 508, a first terminal of capacitor 210, a first terminal of resistor 230, a second terminal of resistor 206, and a first input terminal of fully differential amplifier 204. A second current terminal of transistor 510 is coupled to a second terminal of resistor 502, a second terminal of resistor 506, a second current terminal of transistor 508, a second terminal of capacitor 210, a first output terminal of fully differential amplifier 204, ADC 108, and a first input terminal of lossless integrator 202. A control terminal of transistor 510 is coupled to a second terminal of resistor 504 and a first terminal of resistor 506.

[0051] Figure 5Resistors 512, 514, 516, 518 each have two terminals. A first terminal of resistor 512 is coupled to a first current terminal of transistor 520, a first terminal of resistor 516, a first current terminal of transistor 522, a first terminal of capacitor 212, a first terminal of resistor 232, a second terminal of resistor 208, and a second input terminal of fully differential amplifier 204. A second terminal of resistor 512 is coupled to a first terminal of resistor 514 and a control terminal of transistor 520. A first terminal of resistor 514 is coupled to a second terminal of resistor 512 and a control terminal of transistor 520. A second terminal of resistor 514 is coupled to a second current terminal of transistor 520, a second terminal of resistor 518, a second current terminal of transistor 522, a second terminal of capacitor 212, a second output terminal of fully differential amplifier 204, ADC 108, and a second input terminal of lossless integrator 202. A first terminal of resistor 516 is coupled to a first current terminal of transistor 520, a first terminal of resistor 512, a first current terminal of transistor 522, a first terminal of capacitor 212, a first terminal of resistor 232, a second terminal of resistor 208, and a second input terminal of fully differential amplifier 204. A second terminal of resistor 516 is coupled to a first terminal of resistor 518 and a control terminal of transistor 522. A first terminal of resistor 514 is coupled to a second terminal of resistor 516 and a control terminal of transistor 522. A second terminal of resistor 514 is coupled to a second current terminal of transistor 520, a second terminal of resistor 514, a second current terminal of transistor 522, a second terminal of capacitor 212, a second output terminal of fully differential amplifier 204, ADC 108, and a second input terminal of lossless integrator 202.

[0052] Figure 5The transistors 520, 522 are bipolar junction transistors (BJT). However, the transistors 520, 522 may be metal oxide semiconductor field effect transistors (MOSFET) and / or any other type of transistor. The transistors 520, 522 each have two current terminals (e.g., an emitter terminal and a collector terminal) and a control terminal (e.g., a base terminal). The first current terminal of the transistor 520 is coupled to a terminal of the resistor 512, a first terminal of the resistor 516, a first current terminal of the transistor 522, a first terminal of the capacitor 212, a first terminal of the resistor 232, a second terminal of the resistor 208, and a second input terminal of the fully differential amplifier 204. The second current terminal of the transistor 520 is coupled to a second terminal of the resistor 514, a second terminal of the resistor 518, a second current terminal of the transistor 522, a second terminal of the capacitor 212, a second output terminal of the fully differential amplifier 204, the ADC 108, and a second input terminal of the lossless integrator 202. A control terminal of transistor 520 is coupled to a second terminal of resistor 512 and a first terminal of resistor 514. A first current terminal of transistor 522 is coupled to a terminal of resistor 512, a first terminal of resistor 516, a first current terminal of transistor 508, a first terminal of capacitor 212, a first terminal of resistor 232, a second terminal of resistor 208, and a second input terminal of fully differential amplifier 204. A second current terminal of transistor 522 is coupled to a second terminal of resistor 514, a second terminal of resistor 518, a second current terminal of transistor 520, a second terminal of capacitor 212, a second output terminal of fully differential amplifier 204, ADC 108, and a second input terminal of lossless integrator 202. A control terminal of transistor 522 is coupled to a second terminal of resistor 516 and a first terminal of resistor 518.

[0053] As described above, diode circuitry 214, 222 includes diodes 216, 220, 224, 228. Diodes 216, 228 conduct (e.g., operate as a low impedance short) in response to the input voltage exceeding a first threshold (e.g., 0.7V). In addition, diodes 220, 224 conduct in response to the input voltage falling below a second threshold (e.g., -0.7V). The thresholds are based on characteristics of the diodes. Figure 5 The example diode circuit system 555, 560 is similar to Figure 2-4However, the threshold voltage at which the transistor turns on and operates like a diode can be controlled based on, for example, a function of the selected resistor values ​​501, 502, 504, 506. For example, transistor 508 operates like a diode, where the turn-on voltage is based on, for example, a function of resistors 501, 502. That is, the turn-on voltage is (1+R1 / R2)*VBE, where R1 is the resistance of resistor 501, R2 is the resistance of resistor 502, and VBE is the base emitter voltage of transistor 508.

[0054] In this manner, a user and / or manufacturer can adjust the on-voltage of transistors 508, 510, 520, 522 to cap the input signal to a maximum and / or minimum value based on the specific resistance selected for the corresponding resistors 501, 502, 504, 506, 512, 514, 516, 518. In addition, the resistances of 501, 502, 504, 506 can be selected so that the total feedback resistance is equal to the resistance of resistor 218, for example, to achieve a desired quality value. Similarly, resistors 512, 514, 516, 518 can be selected to control the on-voltage of the corresponding transistors 520, 522 so that the total feedback resistance is equal to the resistance of resistor 226, for example, to achieve a desired quality value. Furthermore, to achieve symmetry of the inverting and non-inverting input signals, the resistance of resistor 512 may be the same as the resistance of resistor 501; the resistance of resistor 514 may be the same as the resistance of resistor 502; the resistance of resistor 516 may be the same as the resistance of resistor 504; and the resistance of resistor 518 may be the same as the resistance of resistor 506. However, the resistances of resistors 501, 502, 504, 506, 512, 514, 516, 518 may be any resistances.

[0055] Figure 6 A circuit implementation for using the lossless integrator 202 is described to implement Figure 5 Example bandpass filter 650 of example bandpass filter 106 . Figure 6 The bandpass filter 650 includes Figure 2 500 and the example lossless integrator 202. Figure 6 The lossy integrator 500 includes Figure 2 The example fully differential amplifier 204, the example resistors 206, 208 and the example feedback capacitors 210, 212 of FIG. The lossy integrator 500 additionally includes Figure 5 Resistors 501 , 502 , 504 , 506 , 512 , 514 , 516 , 518 and transistors 508 , 510 , 520 , 522 and example diode circuitry 555 , 560 . Figure 6 The example bandpass filter 650 additionally includes Figure 2The example lossless integrator 202 includes example resistors 300 , 302 , an example fully differential amplifier 304 , and example capacitors 306 , 308 .

[0056] Figure 7 Instructions for using a differential amplifier to implement Figure 1 Example bandpass filter 750 of example bandpass filter 106 . Figure 7 The bandpass filter 750 includes an example lossy integrator 700 and an example lossless integrator 702 . Figure 7 The lossy integrator 700 includes Figure 5 and / or resistors 206 , 501 , 502 , 504 , 506 , transistors 508 , 510 . Figure 7 The lossy integrator 700 additionally includes Figure 4 The differential amplifier 404 is provided. Figure 7 The lossless integrator 702 includes Figure 3 The lossless integrator 702 further includes a resistor 300 and a capacitor 306. Figure 4 The differential amplifier 406 and the inverter 408 are provided. Figure 7 The bandpass filter 750 additionally includes Figure 2-6 The feedback resistor 230.

[0057] exist Figure 7 In the example lossy integrator 700, resistors 206, 501, 502, 504, 506, capacitor 210, diode circuitry 555, and transistors 508, 510 are connected to Figure 5 6. However, in the lossy integrator 700, the fully differential amplifier 204 is replaced by a differential amplifier 404 (e.g., an operational amplifier, an error amplifier, etc.) and receives only one input signal. The differential amplifier 404 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminal of the differential amplifier 404 is coupled to the second terminal of the resistor 206, the first terminal of the resistor 230, the first current terminal of the transistor 508, the first terminal of the resistor 501, the first terminal of the resistor 504, the first current terminal of the transistor 510, and the first terminal of the capacitor 210. The non-inverting input terminal of the differential amplifier 404 is coupled to the ground. The output terminal of the differential amplifier 404 is coupled to the ADC 108, the first input terminal of the lossless integrator 202, the second current terminal of the transistor 508, the second terminal of the resistor 502, the second terminal of the resistor 506, the second current terminal of the transistor 510, and the second terminal of the capacitor 210.

[0058] exist Figure 7 In the example lossless integrator 702, resistor 300 and capacitor 306 are connected with Figure 3 6. However, in the lossless integrator 702, the fully differential amplifier 304 is replaced by a differential amplifier 406. The differential amplifier 406 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminal of the differential amplifier 406 is coupled to the second terminal of the resistor 300 and the first terminal of the capacitor 306. The non-inverting input terminal of the differential amplifier 406 is coupled to the ground. The output terminal of the differential amplifier 406 is coupled to the second terminal of the capacitor 306 and the second terminal of the input terminal of the inverter 408.

[0059] Figure 8 Description for implementation Figure 1 Example bandpass filter 850 of example bandpass filter 106 . Figure 8 The bandpass filter 106 includes Figure 2 800 and the example lossless integrator 202. Figure 8 The lossy integrator 800 includes Figure 2 An example fully differential amplifier 204 , example resistors 206 , 208 , and example feedback capacitors 210 , 212 . Figure 3 The example bandpass filter 850 further includes Figure 2 The feedback resistors 230, 232 are connected to the Figure 8 In the example diode circuit systems 855, 860, the example resistors 801, 802, 804, 810, 812, 814 and the example transistors 806, 808, 816, 818 are replaced. Figure 2-4 The diodes 216, 220, 224, 228 and the resistors 218, 226 and / or Figure 5-7 Examples of resistors 501 , 502 , 504 , 506 , 512 , 514 , 516 , 518 and transistors 508 , 510 , 520 , 522 .

[0060] Figure 8Resistors 801, 802, 804 each have two terminals. A first terminal of resistor 801 is coupled to a first current terminal of transistor 806, a first current terminal of transistor 808, a first terminal of capacitor 210, a first terminal of resistor 230, a second terminal of resistor 206, and a first input terminal of fully differential amplifier 204. A second terminal of resistor 801 is coupled to a first terminal of resistor 802 and a control terminal of transistor 806. A first terminal of resistor 802 is coupled to a second terminal of resistor 801 and a control terminal of transistor 806. A second terminal of resistor 802 is coupled to a first terminal of resistor 804 and a control terminal of transistor 808. A first terminal of resistor 804 is coupled to a second terminal of resistor 802 and a current terminal of transistor 808. A second terminal of resistor 804 is coupled to a second current terminal of transistor 806, a second current terminal of transistor 808, a second terminal of capacitor 210, a first output terminal of fully differential amplifier 204, ADC 108, and a first input terminal of lossless integrator 202.

[0061] Figure 8 The transistors 806, 808 are bipolar junction transistors (BJT). However, the transistors 806, 808 may be metal oxide semiconductor field effect transistors (MOSFET) and / or any other type of transistor. The transistors 806, 808 each have two current terminals (e.g., an emitter terminal and a collector terminal) and a control terminal (e.g., a base terminal). The first current terminal of the transistor 806 is coupled to a terminal of the resistor 801, a first current terminal of the transistor 808, a first terminal of the capacitor 210, a first terminal of the resistor 230, a second terminal of the resistor 206, and a first input terminal of the fully differential amplifier 204. The second current terminal of the transistor 806 is coupled to a second terminal of the resistor 804, a second current terminal of the transistor 808, a second terminal of the capacitor 210, a first output terminal of the fully differential amplifier 204, the ADC 108, and a first input terminal of the lossless integrator 202. The control terminal of the transistor 806 is coupled to a second terminal of the resistor 801 and a first terminal of the resistor 802. A first current terminal of transistor 808 is coupled to a terminal of resistor 801, a first current terminal of transistor 806, a first terminal of capacitor 210, a first terminal of resistor 230, a second terminal of resistor 206, and a first input terminal of fully differential amplifier 204. A second current terminal of transistor 808 is coupled to a second terminal of resistor 804, a second current terminal of transistor 806, a second terminal of capacitor 210, a first output terminal of fully differential amplifier 204, ADC 108, and a first input terminal of lossless integrator 202. A control terminal of transistor 808 is coupled to a second terminal of resistor 804 and a first terminal of resistor 802.

[0062] Figure 8 Resistors 810, 812, 814 each have two terminals. A first terminal of resistor 810 is coupled to a first current terminal of transistor 816, a first current terminal of transistor 818, a first terminal of capacitor 212, a first terminal of resistor 232, a second terminal of resistor 208, and a second input terminal of fully differential amplifier 204. A second terminal of resistor 810 is coupled to a first terminal of resistor 812 and a control terminal of transistor 816. A first terminal of resistor 812 is coupled to a second terminal of resistor 810 and a control terminal of transistor 816. A second terminal of resistor 812 is coupled to a first terminal of resistor 814 and a control terminal of transistor 818. A first terminal of resistor 814 is coupled to a second terminal of resistor 812 and a current terminal of transistor 818. A second terminal of resistor 814 is coupled to a second current terminal of transistor 816, a second current terminal of transistor 818, a second terminal of capacitor 212, a second output terminal of fully differential amplifier 204, ADC 108, and a second input terminal of lossless integrator 202.

[0063] Figure 8The transistors 816, 818 are bipolar junction transistors (BJT). However, the transistors 816, 818 may be metal oxide semiconductor field effect transistors (MOSFET) and / or any other type of transistor. The transistors 816, 818 each have two current terminals (e.g., an emitter terminal and a collector terminal) and a control terminal (e.g., a base terminal). The first current terminal of the transistor 816 is coupled to a terminal of the resistor 810, a first current terminal of the transistor 818, a first terminal of the capacitor 212, a first terminal of the resistor 232, a second terminal of the resistor 208, and a second input terminal of the fully differential amplifier 204. The second current terminal of the transistor 816 is coupled to a second terminal of the resistor 814, a second current terminal of the transistor 818, a second terminal of the capacitor 212, a second output terminal of the fully differential amplifier 204, the ADC 108, and a second input terminal of the lossless integrator 202. The control terminal of the transistor 816 is coupled to the second terminal of the resistor 810 and the first terminal of the resistor 812. A first current terminal of transistor 818 is coupled to a terminal of resistor 810, a first current terminal of transistor 816, a first terminal of capacitor 212, a first terminal of resistor 232, a second terminal of resistor 208, and a second input terminal of fully differential amplifier 204. A second current terminal of transistor 818 is coupled to a second terminal of resistor 814, a second current terminal of transistor 816, a second terminal of capacitor 212, a second output terminal of fully differential amplifier 204, ADC 108, and a second input terminal of lossless integrator 202. A control terminal of transistor 818 is coupled to a second terminal of resistor 814 and a first terminal of resistor 812.

[0064] As described above, the diode circuit systems 214, 222 include Figure 2-4 The diodes 216, 220, 224, 228 are configured to conduct (e.g., operate as a low impedance short circuit) in response to the input voltage exceeding a first threshold (e.g., 0.7V) or falling below a second threshold (e.g., -0.7V). The thresholds are based on the characteristics of the diodes. Figure 5-7 As described above, resistors 501, 502, 504, 506, 512, 514, 516, 518 and transistors 508, 510, 520, 522 are connected to Figure 2-4 The diode circuit systems 214 , 222 operate in the same manner, where the turn-on voltage can be selected based on the value of the resistance of the resistors 501 , 502 , 504 , 506 , 512 , 514 , 516 , 518 . Figure 8 The example diode circuit systems 855, 860 are shown with Figure 5-7806. The diode circuit systems 855 and 860 operate in the same manner as the diode circuit systems 555 and 560. However, the diode circuit systems 855 and 860 include one less transistor. Therefore, the transistor 806 operates like a diode, where the on-voltage is based on the resistors 801, 802, and 804. For example, the on-voltage is (1+R1 / (R3+R2))*VBE, where R1 is the resistance of the resistor 801, R2 is the resistance of the resistor 802, R3 is the resistance of the resistor 804, and VBE is the base emitter voltage of the transistor 806. In addition, the transistor 808 operates like a diode, where the on-voltage is based on the resistance of the resistors 801, 802, and 804. For example, the on-voltage is (1+R3 / (R1+R2))*VBE, where R1 is the resistance of the resistor 801, R2 is the resistance of the resistor 802, R3 is the resistance of the resistor 804, and VBE is the base emitter voltage of the transistor 806.

[0065] In this manner, a user and / or manufacturer may adjust the on-voltage based on the specific resistance selected for resistors 801, 802, 804, 810, 812, 814 to cap the input signal to a maximum and / or minimum value. Figure 8 In the example of , the resistances of resistors 801 and 804 are the same for symmetry, for example, so that the on-voltage of transistor 806 is opposite to the on-voltage of transistor 808. However, the resistances of resistors 801, 802, 804 can be selected to be any resistance. In addition, the resistances of 801, 802, 804 can be selected so that the total feedback resistance is equal to the resistance of resistor 218, for example, the sum of the resistances of resistors 801, 802, 804 is equal to Figure 2 The resistance of resistor 218 of the embodiment of the present invention can be selected to achieve the desired quality value. Similarly, resistors 810, 812, 814 can be selected to control the turn-on voltage of the corresponding transistors 816, 818, and make the total feedback resistance equal to the resistance of resistor 226, for example, to achieve the desired quality value. In addition, in order to achieve symmetry of the inverting and non-inverting input signals, the resistance of resistor 810 can be the same as the resistance of resistor 801, the resistance of resistor 812 can be the same as the resistance of resistor 802, and the resistance of resistor 814 can be the same as the resistance of resistor 804. However, the resistances of resistors 801, 802, 804, 810, 812, 814 can be any resistance.

[0066] Fig. 9 A circuit implementation for using the lossless integrator 202 is described to implement Figure 8 Example bandpass filter 950 of example bandpass filter 106 . Fig. 9 The bandpass filter 950 includes Figure 8 An example lossy integrator 800 and Figure 2 An example lossless integrator 202 is shown. Fig. 9 The lossy integrator 800 includes Figure 2 The example fully differential amplifier 204, the example resistors 206, 208 and the example feedback capacitors 210, 212. The lossy integrator 800 further includes resistors 801, 802, 804, 810, 812, 814 and transistors 806, 808, 816, 818, and Figure 8 Example diode circuit systems 855, 860. Fig. 9 The example bandpass filter 950 additionally includes Figure 2 The example lossless integrator 202 includes example resistors 300 , 302 , an example fully differential amplifier 304 , and example capacitors 306 , 308 .

[0067] Fig.10 Description of the differential amplifier Figure 1 Example bandpass filter 106 of example bandpass filter 1050 . Fig.10 The bandpass filter 1050 includes an example lossy integrator 1000 and an example lossless integrator 1002 . Fig.10 The lossy integrator 1000 includes Figure 8 and / or resistors 206 , 801 , 802 , 804 , transistors 806 , 808 of 9 . Fig.10 The lossy integrator 1000 additionally includes Figure 4 The differential amplifier 404 is provided. Fig.10 The lossless integrator 1002 includes Figure 3 The lossless integrator 1002 further includes a resistor 300 and a capacitor 306. Figure 4 The differential amplifier 406 and the inverter 408 are provided. Fig.10 The bandpass filter 1050 additionally includes Figure 2-9 The feedback resistor 230.

[0068] exist Fig.10 In the example lossy integrator 1000, resistors 206, 801, 802, 804, capacitor 210, diode circuitry 855, and transistors 806, 808 are connected to Figure 8 and / or 9 in the same manner. However, in the lossy integrator 1000, the fully differential amplifier 204 is Figure 4206, a first terminal of the resistor 230, a first current terminal of the transistor 806, a first terminal of the resistor 801, a first current terminal of the transistor 808, and a first terminal of the capacitor 210. The non-inverting input terminal of the differential amplifier 404 is coupled to the ground. The output terminal of the differential amplifier 404 is coupled to the ADC 108, the first input terminal of the lossless integrator 202, the second current terminal of the transistor 806, the second terminal of the resistor 804, the second current terminal of the transistor 808, and the second terminal of the capacitor 210.

[0069] exist Fig.10 In the example lossless integrator 1002, resistor 300 and capacitor 306 are connected with Figure 3 , 6 9. However, in the lossless integrator 1002, the fully differential amplifier 304 is replaced by a differential amplifier 406. The differential amplifier 406 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminal of the differential amplifier 406 is coupled to the second terminal of the resistor 300 and the first terminal of the capacitor 306. The non-inverting input terminal of the differential amplifier 406 is coupled to the ground. The output terminal of the differential amplifier 406 is coupled to the second terminal of the capacitor 306 and the input terminal of the inverter 408.

[0070] Fig.11 For Figure 1 , 2 , 3, 4, 5, 6, 7, 8, 9 and / or 10, a method and / or a flowchart representation of example operations 1100 performed by a circuit system of a bandpass filter 106, 250, 350, 450, 550, 650, 750, 850, 950, 1050. Although in combination with Figure 1 The bandpass filter 106 in the image scanner 100 is described as follows Fig.11 operation, but can be combined with Figure 2-10 Operation is described with reference to any of the bandpass filters 250, 350, 450, 550, 650, 750, 850, 950, 1050, stand-alone bandpass filters and / or bandpass filters included in any type of circuit system, device and / or system.

[0071] Fig.11 Operations 1100 of the invention begin at block 1102, where Figure 2-10The diode circuit system 214, 222, 555, 560, 855, 860 of any one of the above is used to determine whether the input voltage is above a first threshold. As described above, the first threshold corresponds to a turn-on voltage and can be based on the characteristics of the diodes 220, 228 and / or based on the resistance of the resistors 501, 502, 512, 514, 801, 802, 804, 810, 812, 814. If the input voltage is above the first threshold voltage (block 1102: yes), then the diode circuit system 214, 222, 555, 560, 855, 860 applies a low feedback resistance to move the non-dominant pole to a higher frequency and / or to move the unity gain crossover point to a lower frequency (block 1104). For example, the diodes 220, 228 and / or the transistors 508, 520 are turned on to operate as a low impedance short circuit. In response to diodes 220, 228 and / or transistors 508, 520 turning on, the resistance of the low impedance path is connected in parallel with the resistance of resistors 218, 226, 501, 502, 504, 506, 512, 514, 516, 518, 801, 802, 804, 810, 812, 814, thereby reducing the feedback resistance. As described above, reducing the feedback resistance reduces the gain of the lossy amplifier 200, 400, 500, 700, 800, 1000, moves the non-dominant pole to a higher frequency, and / or moves the unity gain crossover point to a lower frequency. Moving the frequency of the non-dominant pole and the unity gain crossover point increases the stability of the bandpass filter 106.

[0072] If the input voltage is not above the first threshold voltage (block 1102: No), then the diode circuit system 214, 222, 555, 560, 855, 860 applies a high feedback resistance corresponding to the resistance of resistors 218, 226, 501, 502, 504, 506, 512, 514, 516, 518, 801, 802, 804, 810, 812, 814 (block 1106).

[0073] At block 1106, Figure 2-10The diode circuit system 214, 222, 555, 560, 855, 860 of any one of the above is used to determine whether the input voltage is below a second threshold. As described above, the second threshold corresponds to a turn-on voltage and can be based on the characteristics of the diodes 216, 224 and / or based on the resistance of the resistors 504, 506, 516, 518, 801, 802, 804, 810, 812, 814. If the input voltage is below the second threshold voltage (block 1106: yes), then the diode circuit system 214, 222, 555, 560, 855, 860 applies a low feedback resistance to move the non-dominant pole to a higher frequency and / or to move the unity gain crossover point to a lower frequency (block 1108). For example, the diodes 216, 224 and / or the transistors 510, 522 are turned on to operate as a low impedance short circuit. In response to diodes 216, 224 and / or transistors 510, 522 turning on, the resistance of the low impedance path is connected in parallel with the resistance of resistors 218, 226, 501, 502, 504, 506, 512, 514, 516, 518, 801, 802, 804, 810, 812, 814, thereby reducing the feedback resistance. As described above, reducing the feedback resistance reduces the gain of the lossy amplifier 200, 400, 500, 700, 800, 1000, moves the non-dominant pole to a higher frequency, and / or moves the unity gain crossover point to a lower frequency. Moving the frequency of the non-dominant pole and the unity gain crossover point increases the stability of the bandpass filter 106. After block 1108, control returns to block 1102.

[0074] If the input voltage is not below the second threshold voltage (block 1108: No), the diode circuit system 214, 222, 555, 560, 855, 860 applies a high feedback resistance corresponding to the resistance of the resistors 218, 226, 501, 502, 504, 506, 512, 514, 516, 518, 801, 802, 804, 810, 812, 814 (block 1112). After block 1112, control returns to block 1102.

[0075] Fig.12 To illustrate an example overload input signal 1202, without Figure 2-10 Example bandpass filter output 1204 of diode circuit system 214, 222, 555, 560, 855, 860 and having Figure 2-10 An example timing diagram 1200 of an example bandpass filter output 1206 of any of the diode circuit systems 214, 222, 555, 560, 855, 860.

[0076] The example overload input signal 1202 starts with a signal of 4 times the expected amplitude of the output of the front end amplification state circuit system 104. The overload input signal 1202 is then reduced to a manageable amplitude. As shown in the example bandpass filter output 1204, the output signal oscillates due to the overload input signal 1202 and does not recover even after the overload input signal 1202 is reduced to a manageable amplitude. Therefore, the bandpass filter without the diode circuit system 214, 222, 555, 560, 855, 860 is an unstable system in response to the overload input signal 1202 applied to the corresponding bandpass filter. As shown in the example bandpass filter output 1206, the output signal oscillates with the overload input signal 1202 and recovers after the overload input signal 1202 is reduced to a manageable amplitude. Thus, the bandpass filter 106 with the diode circuitry 214 , 222 , 555 , 560 , 855 , 860 described herein is a stable system in response to an applied overload input signal 1202 .

[0077] accomplish Figure 1 An example embodiment of the bandpass filter 106 is shown in Figure 2 However, Figure 2-10 One or more of the elements, processes, and / or devices described in the drawings may be combined, divided, rearranged, omitted, eliminated, and / or implemented in any other manner.

[0078] in addition, Figure 2-10 A component may include one or more elements, processes and / or devices as Figure 2-10 The present invention may be in addition to or replace the elements, processes and / or devices described in the present invention, and / or may include more than one of any or all of the elements, processes and devices described. As used herein, the phrase "in communication" includes variations thereof, covers direct communication and / or indirect communication through one or more intermediate components, and does not require direct physical (e.g., wired) communication and / or continuous communication, but also includes selective communication at periodic intervals, predetermined intervals, non-periodic intervals and / or one-time events.

[0079] In addition, although the reference Fig.11 The flowcharts illustrated in describe example operations, but many other methods of implementing bandpass filters 106, 250, 350, 450, 550, 650, 750, 850, 950, 1050 may alternatively be used. For example, the order of the blocks may be changed, and / or some of the blocks described may be changed, eliminated, or combined.

[0080] Descriptors "first," "second," "third," etc., are used herein when identifying multiple elements or components that can be referred to individually. Unless otherwise specified or understood based on the context of their use, such descriptors are not attributed any meaning of priority, physical order, or arrangement in a list or chronological order, but are merely used as labels for referring to multiple elements or components individually to facilitate understanding of the described examples. In some examples, the descriptor "first" may be used to refer to an element in the detailed description, while the same element may be referred to in the claims using different descriptors such as "second" or "third." In this case, it should be understood that such descriptors are only used to facilitate reference to multiple elements or components.

[0081] In the specification and claims, unless otherwise stated, the terms "including" and "having" and variations thereof are intended to be inclusive in a manner similar to the term "comprising". Unless otherwise specified, "about", "approximately" or "substantially" before a value means within + / -10% of the value. In another example, "about", "approximately" or "substantially" before a value means within + / -5% of the value. In another example, "about", "approximately" or "substantially" before a value means within + / -1% of the value.

[0082] As used herein, the terms "couple", "coupled", "couples", and variations thereof may encompass connections, communications, or signal paths that enable a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then in a first example, device A is coupled to device B, or in a second example, if the intermediate component C does not substantially change the functional relationship between device A and device B, then device A is coupled to device B through the intermediate component C, such that device B is controlled by device A via the control signal generated by device A. In addition, the terms "couple", "coupled", "couples", or variations thereof include indirect or direct electrical or mechanical connections.

[0083] A device "configured to" perform a task or function may be configured (e.g., programmed and / or hardwired) to perform the function when manufactured by a manufacturer and / or may be configured (or reconfigurable) by a user after manufacture to perform the function and / or other additional or alternative functions. Configuration may be performed through firmware and / or software programming of the device, through the construction and / or layout of the device's hardware components and interconnections, or a combination thereof.

[0084] Although not all are individually labeled in the figures, the components or elements of the systems and circuits described therein have one or more conductors or terminals that allow signals to enter and / or leave the components or elements. Conductors or terminals (or portions thereof) may be referred to herein as pins, pads, terminals (including, for example, input terminals, output terminals, reference terminals, and ground terminals), inputs, outputs, nodes, and interconnects.

[0085] As used herein, the "terminal" of a component, device, system, circuit, integrated circuit or other electronic or semiconductor component generally refers to a conductor, such as a wire, trace, pin, pad or other connector or interconnection that enables a component, device, system, etc. to be electrically and / or mechanically connected to another component, device, system, etc. For example, a terminal can be used to receive or provide an analog or digital electrical signal (or simply referred to as a signal) or be electrically connected to a common or ground reference. Therefore, an input terminal or input is used to receive a signal from another component, device, system, etc. An output terminal or output is used to provide a signal 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 a ground terminal. The terminal of an IC or PCB may also be referred to as a pin (longitudinal conductor) or a pad (planar conductor). A node refers to a connection point or interconnection point of two or more terminals. An example number of terminals and nodes may be shown. However, depending on a specific circuit or system topology, there may be more or fewer terminals and nodes. However, in some cases, "terminals", "nodes", "interconnections", "pads" and "pins" may be used interchangeably.

[0086] The examples described may be modified, and other examples may be modified, within the scope of the claims.

Claims

1. A circuit comprising: an amplifier having an input terminal and an output terminal; a capacitor having a first terminal and a second terminal, the first terminal of the capacitor being coupled to the input terminal of the amplifier and the second terminal of the capacitor being coupled to the output terminal of the amplifier; and A diode circuit system having a first terminal coupled to the first terminal of the capacitor and the input terminal of the amplifier and a second terminal coupled to the second terminal of the capacitor and the output terminal of the amplifier.

2. The circuit of claim 1 , wherein the diode circuit system comprises: a resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the input terminal of the amplifier and the first terminal of the capacitor, the second terminal of the resistor being coupled to the output terminal of the amplifier and the second terminal of the capacitor; a first diode having an anode terminal and a cathode terminal, the anode terminal of the first diode being coupled to the first terminal of the resistor, the first terminal of the capacitor, and the input terminal of the amplifier, and the cathode terminal of the first diode being coupled to the second terminal of the resistor, the second terminal of the capacitor, and the output terminal of the amplifier; and a second diode having an anode terminal and a cathode terminal, the cathode terminal of the second diode being coupled to the first terminal of the resistor, the first terminal of the capacitor, and the input terminal of the amplifier, and the anode terminal of the second diode being coupled to the second terminal of the resistor, the second terminal of the capacitor, and the output terminal of the amplifier.

3. The circuit of claim 1 , wherein the diode circuit system comprises: a first resistor having a first terminal and a second terminal; the first terminal of the first resistor being coupled to the first terminal of the capacitor and to the input terminal of the amplifier; a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the second terminal of the first resistor, the second terminal of the second resistor being coupled to the second terminal of the capacitor and the output terminal of the amplifier; and a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor being coupled to the first terminal of the first resistor, the first terminal of the capacitor, and the input terminal of the amplifier, the second current terminal of the transistor being coupled to the second terminal of the second resistor, the second terminal of the capacitor, and the output terminal of the amplifier, and the control terminal of the transistor being coupled to the second terminal of the first resistor and the first terminal of the second resistor.

4. The circuit of claim 3, wherein the transistor is a first transistor, the diode circuitry further comprising: a third resistor having a first terminal and a second terminal; the first terminal of the third resistor being coupled to the first terminal of the capacitor, the input terminal of the amplifier, the first terminal of the first resistor, and the first current terminal of the first transistor; a fourth resistor having a first terminal and a second terminal, the first terminal of the fourth resistor being coupled to the second terminal of the third resistor, the second terminal of the fourth resistor being coupled to the second terminal of the capacitor, the output terminal of the amplifier, the second terminal of the second resistor, and the second current terminal of the first transistor; and 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 terminal of the first resistor, the first terminal of the third resistor, the first current terminal of the first transistor, the first terminal of the capacitor and the input terminal of the amplifier, the second current terminal of the second transistor being coupled to the second terminal of the second resistor, the second terminal of the fourth resistor, the second current terminal of the first transistor, the second terminal of the capacitor and the output terminal of the amplifier, and the control terminal of the second transistor being coupled to the second terminal of the third resistor and the first terminal of the fourth resistor.

5. The circuit of claim 1 , wherein the diode circuit system comprises: a first resistor having a first terminal and a second terminal; the first terminal of the first resistor being coupled to the first terminal of the capacitor and to the input terminal of the amplifier; a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the second terminal of the first resistor; a third resistor having a first terminal and a second terminal, the first terminal of the third resistor being coupled to the second terminal of the second resistor, the second terminal of the third resistor being coupled to the second terminal of the capacitor and the output terminal of the amplifier; and a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor being coupled to the first terminal of the first resistor, the first terminal of the capacitor, and the input terminal of the amplifier, the second current terminal of the transistor being coupled to the second terminal of the third resistor, the second terminal of the capacitor, and the output terminal of the amplifier, and the control terminal of the transistor being coupled to the second terminal of the first resistor and the first terminal of the second resistor.

6. The circuit of claim 5 , wherein the transistor is a first transistor, the diode circuit system further comprising 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 terminal of the first resistor, the first current terminal of the first transistor, the first terminal of the capacitor, and the input terminal of the amplifier, the second current terminal of the second transistor being coupled to the second terminal of the third resistor, the second current terminal of the first transistor, the second terminal of the capacitor, and the output terminal of the amplifier, and the control terminal of the second transistor being coupled to the second terminal of the second resistor and the first terminal of the third resistor.

7. A bandpass filter, comprising: a lossless integrator having an input terminal and an output terminal; A lossy integrator having an input terminal and an output terminal, the input terminal of the lossy integrator being coupled to the output terminal of the lossless integrator, the output terminal of the lossy integrator being coupled to the input terminal of the lossless integrator, the lossy integrator comprising: an amplifier having an input terminal and an output terminal; and Diode circuitry is coupled to the input terminal of the amplifier and the output terminal of the amplifier.

8. The bandpass filter according to claim 7, wherein: The lossy integrator includes a capacitor having a first terminal and a second terminal; and The diode circuit system comprises: a resistor having a first terminal and a second terminal, the first terminal of the resistor being coupled to the input terminal of the amplifier and the first terminal of the capacitor, the second terminal of the resistor being coupled to the output terminal of the amplifier and the second terminal of the capacitor; a first diode having an anode terminal and a cathode terminal, the anode terminal of the first diode being coupled to the first terminal of the resistor, the first terminal of the capacitor, and the input terminal of the amplifier, the cathode terminal of the first diode being coupled to the second terminal of the resistor, the second terminal of the capacitor, and the output terminal of the amplifier; and a second diode having an anode terminal and a cathode terminal, the cathode terminal of the second diode being coupled to the first terminal of the resistor, the first terminal of the capacitor, and the input terminal of the amplifier, and the anode terminal of the second diode being coupled to the second terminal of the resistor, the second terminal of the capacitor, and the output terminal of the amplifier.

9. The bandpass filter according to claim 7, wherein: The lossy integrator includes a capacitor having a first terminal and a second terminal; and The diode circuit system comprises: a first resistor having a first terminal and a second terminal; the first terminal of the first resistor being coupled to the first terminal of the capacitor and the input terminal of the amplifier; a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the second terminal of the first resistor, the second terminal of the second resistor being coupled to the second terminal of the capacitor and the output terminal of the amplifier; and a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor being coupled to the first terminal of the first resistor, the first terminal of the capacitor, and the input terminal of the amplifier, the second current terminal of the transistor being coupled to the second terminal of the second resistor, the second terminal of the capacitor, and the output terminal of the amplifier, and the control terminal of the transistor being coupled to the second terminal of the first resistor and the first terminal of the second resistor.

10. The bandpass filter according to claim 7, wherein: The lossy integrator includes a capacitor having a first terminal and a second terminal; and The diode circuit system comprises: a first resistor having a first terminal and a second terminal; the first terminal of the first resistor being coupled to the first terminal of the capacitor and the input terminal of the amplifier; a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the second terminal of the first resistor; a third resistor having a first terminal and a second terminal, the first terminal of the third resistor being coupled to the second terminal of the second resistor, the second terminal of the third resistor being coupled to the second terminal of the capacitor and the output terminal of the amplifier; and a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor being coupled to the first terminal of the first resistor, the first terminal of the capacitor, and the input terminal of the amplifier, the second current terminal of the transistor being coupled to the second terminal of the third resistor, the second terminal of the capacitor, and the output terminal of the amplifier, and the control terminal of the transistor being coupled to the second terminal of the first resistor and the first terminal of the second resistor.

11. A filter circuit, comprising: an amplifier configured to amplify an input voltage based on a feedback resistance between an input and an output of the amplifier; and Diode circuitry is coupled between the input and output of the amplifier, the diode circuitry being configured to reduce the feedback resistance when the input voltage is above a threshold. 12 . The filter circuit of claim 11 , wherein the threshold is a first threshold, and the diode circuit system is configured to reduce the feedback resistance when the input voltage is lower than a second threshold.

13. The filter circuit of claim 11, wherein the diode circuitry is configured to reduce the feedback resistance in response to being turned on.

14. The filter circuit of claim 11, wherein the diode circuitry is configured to increase the feedback resistance when the input voltage is below the threshold.

15. A circuit comprising: an amplifier having an inverting input terminal, a non-inverting input terminal, and an inverting output terminal and a non-inverting output terminal; a first capacitor having a first terminal and a second terminal, the first terminal of the first capacitor being coupled to the inverting input terminal of the amplifier, the second terminal of the first capacitor being coupled to the non-inverting output terminal of the amplifier; a first diode circuit system having a first terminal and a second terminal, the first terminal of the first diode circuit system being coupled to the first terminal of the first capacitor and the inverting input terminal of the amplifier, the second terminal of the first diode circuit system being coupled to the second terminal of the first capacitor and the non-inverting output terminal of the amplifier; a second capacitor having a first terminal and a second terminal, the first terminal of the second capacitor being coupled to the non-inverting input terminal of the amplifier and the second terminal of the second capacitor being coupled to the inverting output terminal of the amplifier; and a second diode circuit system having a first terminal and a second terminal, wherein the first terminal of the second diode circuit system is coupled to the first terminal of the second capacitor and the non-inverting input terminal of the amplifier, and the second terminal of the second diode circuit system is coupled to the second terminal of the second capacitor and the inverting output terminal of the amplifier.

16. The circuit of claim 15 , further comprising a lossless integrator having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, the first input terminal of the lossless integrator being coupled to the non-inverting output terminal of the amplifier, the second input terminal of the lossless integrator being coupled to the inverting output terminal of the amplifier, the first output terminal of the lossless integrator being coupled to the inverting input terminal of the amplifier via a first resistor, and the second output terminal of the lossless integrator being coupled to the non-inverting input terminal of the amplifier via a second resistor.

17. The circuit of claim 15, wherein the first diode circuit system comprises: a resistor having a first terminal coupled to the inverting input terminal of the amplifier and the first terminal of the first capacitor and a second terminal coupled to the non-inverting output terminal of the amplifier and the second terminal of the first capacitor; a first diode having an anode terminal and a cathode terminal, the anode terminal of the first diode being coupled to the first terminal of the resistor, the first terminal of the first capacitor, and the inverting input terminal of the amplifier, the cathode terminal of the first diode being coupled to the second terminal of the resistor, the second terminal of the first capacitor, and the non-inverting output terminal of the amplifier; and a second diode having an anode terminal and a cathode terminal, the cathode terminal of the second diode being coupled to the first terminal of the resistor, the first terminal of the first capacitor, and the inverting input terminal of the amplifier, and the anode terminal of the second diode being coupled to the second terminal of the resistor, the second terminal of the first capacitor, and the non-inverting output terminal of the amplifier.

18. The circuit of claim 15, wherein the first diode circuit system comprises: a first resistor having a first terminal and a second terminal; the first terminal of the first resistor being coupled to the first terminal of the first capacitor and to the inverting input terminal of the amplifier; a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the second terminal of the first resistor, the second terminal of the second resistor being coupled to the second terminal of the first capacitor and the non-inverting output terminal of the amplifier; and a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor being coupled to the first terminal of the first resistor, the first terminal of the first capacitor, and the inverting input terminal of the amplifier, the second current terminal of the transistor being coupled to the second terminal of the second resistor, the second terminal of the first capacitor, and the non-inverting output terminal of the amplifier, and the control terminal of the transistor being coupled to the second terminal of the first resistor and the first terminal of the second resistor.

19. The circuit of claim 18, wherein the transistor is a first transistor, the first diode circuitry further comprising: a third resistor having a first terminal and a second terminal; the first terminal of the third resistor being coupled to the first terminal of the first capacitor, the inverting input terminal of the amplifier, the first terminal of the first resistor, and the first current terminal of the first transistor; a fourth resistor having a first terminal and a second terminal, the first terminal of the fourth resistor being coupled to the second terminal of the third resistor, the second terminal of the fourth resistor being coupled to the second terminal of the first capacitor, the non-inverting output terminal of the amplifier, the second terminal of the second resistor, and the second current terminal of the first transistor; and 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 terminal of the first resistor, the first terminal of the third resistor, the first current terminal of the first transistor, the first terminal of the first capacitor and the inverting input terminal of the amplifier, the second current terminal of the second transistor being coupled to the second terminal of the second resistor, the second terminal of the fourth resistor, the second current terminal of the first transistor, the second terminal of the first capacitor and the non-inverting output terminal of the amplifier, and the control terminal of the second transistor being coupled to the second terminal of the third resistor and the first terminal of the fourth resistor.

20. The circuit of claim 15, wherein the first diode circuitry comprises: a first resistor having a first terminal and a second terminal; the first terminal of the first resistor being coupled to the first terminal of the first capacitor and to the inverting input terminal of the amplifier; a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being coupled to the second terminal of the first resistor; a third resistor having a first terminal and a second terminal, the first terminal of the third resistor being coupled to the second terminal of the second resistor, the second terminal of the third resistor being coupled to the second terminal of the first capacitor and the non-inverting output terminal of the amplifier; and a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor being coupled to the first terminal of the first resistor, the first terminal of the first capacitor, and the inverting input terminal of the amplifier, the second current terminal of the transistor being coupled to the second terminal of the third resistor, the second terminal of the first capacitor, and the non-inverting output terminal of the amplifier, and the control terminal of the transistor being coupled to the second terminal of the first resistor and the first terminal of the second resistor.

Images