A capacitor cross-feedback differential amplifier circuit and electronic device

Abstract

This invention belongs to the field of differential amplifier circuit technology and discloses a capacitor cross-feedback differential amplifier circuit and electronic device. The circuit includes a first operational amplifier, a second operational amplifier, a first capacitor, a second capacitor, and a fourth resistor. The non-inverting input terminal of the first operational amplifier is electrically connected to the positive terminal of the analog differential signal input. One end of the first capacitor is electrically connected to the non-inverting input terminal of the first operational amplifier, and the other end is electrically connected to the output terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is electrically connected to the negative terminal of the analog differential signal input. One end of the second capacitor is electrically connected to the non-inverting input terminal of the second operational amplifier, and the other end is electrically connected to the output terminal of the first operational amplifier. The fourth resistor is placed between the inverting input terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier, changing the transmission path of internal noise in the first and second operational amplifiers and reducing the total integrated noise of the output.

Description

Technical Field

[0001] This invention belongs to the field of differential amplifier circuit technology, and relates to a capacitor cross-feedback differential amplifier circuit and electronic equipment. Background Technology

[0002] In the analog front-end of the six-dimensional force sensor, a differential input stage architecture with two operational amplifiers is adopted. The non-inverting inputs of the two operational amplifiers are respectively connected to an RC filter network consisting of resistors, capacitors to ground, and differential-mode capacitors to achieve anti-aliasing filtering and bandwidth limiting, and suppress high-frequency interference.

[0003] In a differential input stage architecture, the gain of the op-amp's own voltage noise is always equal to the gain of the useful differential signal. In a traditional resistive feedback differential amplifier, this causes the intrinsic noise generated by the circuit to be amplified proportionally, making it impossible to distinguish through topology design. When the signal gain is high, the op-amp's voltage noise, current noise, and the resistor's thermal noise are all amplified proportionally, limiting the maximum signal-to-noise ratio.

[0004] To suppress external interference, a large-capacity capacitor is used at the non-inverting input. Although this can effectively filter out high-frequency noise, the low-pass filter formed by the capacitor and the input resistor will significantly compress the signal bandwidth and reduce the dynamic response capability of the sensor. In addition, the large-capacity capacitor occupies a lot of PCB space, which is not conducive to multi-channel integration and miniaturization design. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a capacitor cross-feedback differential amplifier circuit and electronic device.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a capacitor cross-feedback differential amplifier circuit, including a first operational amplifier, a second operational amplifier, a first capacitor, a second capacitor, and a fourth resistor. The non-inverting input terminal of the first operational amplifier is electrically connected to the positive terminal of the analog differential signal input. One end of the first capacitor is electrically connected to the non-inverting input terminal of the first operational amplifier, and the other end is electrically connected to the output terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is electrically connected to the negative terminal of the analog differential signal input. One end of the second capacitor is electrically connected to the non-inverting input terminal of the second operational amplifier, and the other end is electrically connected to the output terminal of the first operational amplifier. The fourth resistor is disposed between the inverting input terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier.

[0007] Furthermore, it also includes a third resistor and a fifth resistor. One end of the third resistor is electrically connected to the inverting input terminal of the first operational amplifier, and the other end is electrically connected to the output terminal of the first operational amplifier. One end of the fifth resistor is electrically connected to the inverting input terminal of the second operational amplifier, and the other end is electrically connected to the output terminal of the second operational amplifier.

[0008] Furthermore, it also includes a first resistor and a second resistor. One end of the first resistor is electrically connected to the positive terminal of the differential signal input, and the other end is electrically connected to the non-inverting input terminal of the first operational amplifier. One end of the second resistor is electrically connected to the analog differential signal, and the other end is electrically connected to the non-inverting input terminal of the second operational amplifier.

[0009] Furthermore, the first resistor and the second resistor have the same resistance value, the third resistor and the fifth resistor have the same resistance value, and the first capacitor and the second capacitor have the same capacitance value.

[0010] Furthermore, the operational amplifier zero-point frequency of the capacitor cross-feedback differential amplifier circuit is greater than the cutoff frequency of the analog differential signal.

[0011] Furthermore, the operational amplifier zero-point frequency of the capacitor cross-feedback differential amplifier circuit is... :

[0012] in, This refers to the capacitance value of either the first or second capacitor. This refers to the resistance value of either the first or second resistor.

[0013] Furthermore, the cutoff frequency of the analog differential signal is :

[0014] in, This refers to the capacitance value of either the first or second capacitor. The resistance value of the first or second resistor. This refers to the resistance value of the third or fifth resistor. This is the resistance value of the fourth resistor.

[0015] Furthermore, the op-amp zero frequency of the capacitor cross-feedback differential amplifier circuit is calculated based on the op-amp voltage noise transfer function, and the noise gain zero term in the op-amp voltage noise transfer function is set to 0. The operational amplifier voltage noise transfer function is: :

[0016] in, For DC gain, This refers to the resistance value of the third or fifth resistor. This is the resistance value of the fourth resistor. The resistance value of the first or second resistor. This refers to the capacitance value of either the first or second capacitor. For complex frequencies, This is the zero-point term of the noise gain.

[0017] Furthermore, the DC gain for:

[0018] in, This is the resistance value of the third resistor. This is the resistance value of the fourth resistor. This is the resistance value of the fourth resistor.

[0019] The present invention also provides an electronic device, including an analog differential signal input terminal, an operational amplifier reference voltage source, an ADC differential input terminal, and the aforementioned capacitor cross-feedback differential amplifier circuit. The positive terminal of the analog differential signal input terminal is connected to one end of a first resistor, and the negative terminal is connected to one end of a second resistor. The positive terminal of the operational amplifier reference voltage source is connected to the power input pins of the first operational amplifier and the second operational amplifier, and the negative terminal is connected to the analog reference ground plane. The positive terminal of the ADC differential input terminal is connected to the differential output positive terminal of the capacitor cross-feedback differential amplifier circuit, and the negative terminal of the ADC differential input terminal is connected to the power input pin of the capacitor cross-feedback differential amplifier circuit.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a capacitor cross-feedback differential amplifier circuit. The non-inverting input of a first operational amplifier is electrically connected to the positive terminal of the analog differential signal input, and the non-inverting input of a second operational amplifier is also electrically connected to the analog differential signal input, ensuring that each operational amplifier receives its corresponding differential signal. A first capacitor and a second capacitor are cross-connected; one end of the first capacitor is electrically connected to the non-inverting input of the first operational amplifier, and the other end is electrically connected to the output of the second operational amplifier. Similarly, one end of the second capacitor is electrically connected to the non-inverting input of the second operational amplifier, and the other end is electrically connected to the output of the first operational amplifier. This introduces a noise gain zero term into the operational amplifier voltage noise transfer function, suppressing the inherent noise of both the first and second operational amplifiers, improving the signal-to-noise ratio of the output signal, and preventing noise interference from affecting signal amplification accuracy. A fourth resistor is placed between the inverting inputs of the first and second operational amplifiers to reduce input offset deviation between the two operational amplifiers and prevent output distortion caused by offset deviation.

[0021] The first and second resistors limit the current input to the non-inverting inputs of the first and second operational amplifiers, preventing damage from excessive input current and providing protection. They also match the impedance of the input signal source with the circuit's input impedance, reducing reflection and attenuation during signal transmission and ensuring accurate transmission of the input signal to the first and second operational amplifiers. The first and second resistors have the same resistance value; any deviation in resistance value will result in inconsistent input signal amplitudes, causing gain imbalance, affecting amplification accuracy, and reducing the circuit's common-mode rejection ratio.

[0022] If the first and second capacitors have the same capacitance value, and the two capacitance values ​​are different, the zero-point frequencies that should coincide in the operational amplifier voltage noise transfer function are split into two different frequency points, generating a noise peak in the frequency band between the two zeros, thus amplifying the noise in that frequency band.

[0023] The op-amp zero-point frequency is calculated based on the op-amp voltage noise transfer function. The noise gain zero-point term is set to zero, and the op-amp zero-point frequency is greater than the cutoff frequency of the analog differential signal. This ensures that the noise gain is always in the falling or concave segment, and the noise gain is lower than the low-frequency DC gain. This suppresses the op-amp's own voltage noise and improves the circuit signal-to-noise ratio and signal amplification purity. It ensures that the analog differential signal is amplified normally within the operating bandwidth, while avoiding excessive amplification of noise within the signal band. Attached Figure Description

[0024] Figure 1 This is a circuit diagram of a capacitor cross-feedback differential amplifier circuit according to the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] This invention shapes the voltage noise of the operational amplifier itself by using a first and second capacitor that are cross-connected. It introduces a designable zero into the voltage noise transfer function of the operational amplifier to suppress noise components, thus maintaining the amplifier's native characteristics while amplifying the differential signal.

[0027] The first capacitor is abbreviated as C1, which indicates the capacitor element numbered 1 in the circuit.

[0028] The second capacitor is abbreviated as C2, which refers to the capacitor element numbered 2 in the circuit.

[0029] The first operational amplifier is abbreviated as A1, which indicates the operational amplifier numbered 1 in the circuit.

[0030] The second operational amplifier is abbreviated as A2, which indicates the operational amplifier numbered 2 in the circuit.

[0031] The first resistor is abbreviated as R1, which indicates the resistor element numbered 1 in the circuit.

[0032] The second resistor is abbreviated as R2, which indicates the resistor element numbered 2 in the circuit.

[0033] The third resistor is abbreviated as R3, which indicates the resistor element numbered 3 in the circuit.

[0034] The fourth resistor is abbreviated as R4, which indicates the resistor element numbered 4 in the circuit.

[0035] The fifth resistor is abbreviated as R5, which indicates the resistor element numbered 5 in the circuit.

[0036] Example 1 This invention discloses a capacitor cross-feedback differential amplifier circuit, comprising: a first operational amplifier, a second operational amplifier, a first capacitor, a second capacitor, and a fourth resistor. The non-inverting input terminal of the first operational amplifier is electrically connected to the positive terminal of the analog differential signal input. One end of the first capacitor is electrically connected to the non-inverting input terminal of the first operational amplifier, and the other end is electrically connected to the output terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is electrically connected to the negative terminal of the analog differential signal input. One end of the second capacitor is electrically connected to the non-inverting input terminal of the second operational amplifier, and the other end is electrically connected to the output terminal of the first operational amplifier. The fourth resistor is disposed between the inverting input terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier.

[0037] Specifically, such as Figure 1 As shown, a capacitor cross-feedback differential amplifier circuit includes a first resistor, a second resistor, a first operational amplifier, a second operational amplifier, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, and a second capacitor. One end of the first resistor is electrically connected to the positive terminal of the differential signal input, and the other end is electrically connected to the non-inverting input terminal of the first operational amplifier. One end of the second resistor is electrically connected to the analog differential signal, and the other end is electrically connected to the non-inverting input terminal of the second operational amplifier. One end of the first capacitor is electrically connected to the non-inverting input terminal of the first operational amplifier, and the other end is electrically connected to the output terminal of the second operational amplifier. One end of the second capacitor is electrically connected to the non-inverting input terminal of the second operational amplifier, and the other end is electrically connected to the output terminal of the first operational amplifier. A fourth resistor is disposed between the inverting input terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier.

[0038] The non-inverting input of the first operational amplifier is electrically connected to the positive input of the differential signal, receiving the positive half of the differential signal to be amplified; the non-inverting input of the second operational amplifier is electrically connected to the negative half of the analog differential signal, forming a symmetrical structure with the first operational amplifier, respectively performing preliminary amplification of the received signals, and then performing signal interaction and noise suppression through cross feedback, finally outputting the amplified differential signal.

[0039] The first and second capacitors are cross-connected. Through the cross feedback between the first and second capacitors, a noise gain zero term is introduced into the operational amplifier voltage noise transfer function, which suppresses the noise of the operational amplifier itself and thus improves the noise performance of the circuit.

[0040] The fourth resistor is placed between the inverting input terminals of the first and second operational amplifiers to reduce input offset deviation of the first and second operational amplifiers, ensuring that the differential amplifier circuit can stably and accurately amplify the input differential signal.

[0041] The first and second resistors limit the current input to the non-inverting input terminals of the first and second operational amplifiers, preventing damage from excessive input current and providing protection. They also match the impedance of the input signal source with the circuit's input impedance, reducing reflection and attenuation during signal transmission and ensuring accurate signal delivery to the first and second operational amplifiers. The third and fifth resistors are inverting input bias resistors, working in conjunction with the fourth resistor to ensure the first and second operational amplifiers operate in the linear amplification region, adjusting the differential gain of the circuit.

[0042] The first resistor and the second resistor have the same resistance value, the third resistor and the fifth resistor have the same resistance value, and the first capacitor and the second capacitor have the same capacitance value.

[0043] In this embodiment, the first and second resistors have a resistance of 50Ω, which is suitable for high-frequency differential signal input scenarios, reducing signal loss and interference during transmission. The first and second resistors have the same resistance value; if there is a deviation in the resistance value, the input signal amplitude will be inconsistent, resulting in gain imbalance, affecting amplification accuracy, and reducing the circuit's common-mode rejection ratio. If the resistance values ​​of the first and second resistors deviate, the positive and negative halves of the input signal will be amplified with different gains, thus causing gain imbalance.

[0044] The third and fifth resistors have a resistance of 2kΩ, and the fourth resistor has a resistance of 10Ω. The first and second capacitors have the same capacitance. If the two capacitances are different, the zero-point frequencies that should coincide in the operational amplifier's voltage noise transfer function will split into two different frequency points, generating a noise peak in the frequency band between the two zeros. This causes the noise in that frequency band to be amplified rather than attenuated.

[0045] The first and second operational amplifiers contain equivalent input voltage noise sources, typically manifesting as a superposition of white noise and low-frequency flicker noise. The white noise primarily consists of thermal noise from internal resistors and shot noise generated by the active region of the transistors, with a power spectral density that is essentially flat across the entire frequency band. The low-frequency flicker noise is mainly generated by poor contact in the internal transistor PN junctions, and its power spectral density increases as the frequency decreases. In traditional differential amplifiers, this internal noise is transmitted to the output through the amplification path, resulting in a reduced signal-to-noise ratio after noise gain amplification, thus affecting the accuracy of signal detection and processing. This invention addresses this by cross-connecting the first and second capacitors, allowing each operational amplifier's non-inverting input to receive feedback not only from its own output but also from the output of the other operational amplifier via the cross-connected capacitors.

[0046] The first and second capacitors are cross-connected; that is, the first capacitor connects to the non-inverting input of the first operational amplifier and the output of the second operational amplifier, and the second capacitor connects to the non-inverting input of the second operational amplifier and the output of the first operational amplifier. A zero-point term for noise gain is introduced into the operational amplifier voltage noise transfer function. This zero-point term alters the amplitude-frequency response of the noise transfer function, thus achieving noise suppression. Through small-signal modeling and Laplace transform analysis, the operational amplifier voltage noise transfer function can be obtained, accurately reflecting the noise signal propagation pattern.

[0047] The op-amp voltage noise transfer function is :

[0048] in, For DC gain, This refers to the resistance value of the third or fifth resistor. This is the resistance value of the fourth resistor. The resistance value of the first or second resistor. This refers to the capacitance value of either the first or second capacitor. For complex frequencies, This is the zero-point term of the noise gain.

[0049] DC gain for:

[0050] in, This is the resistance value of the third resistor. This is the resistance value of the fourth resistor. This is the resistance value of the fourth resistor.

[0051] In the operational amplifier voltage noise transfer function, let the noise gain zero-point term be zero, that is... At this point, the amplitude-frequency characteristic of the operational amplifier's voltage noise transfer function undergoes a reversal, forming a zero-frequency. Below the zero-frequency, the noise gain increases with decreasing frequency, exhibiting a rising characteristic similar to an integrator; near the zero-frequency, the gain curve bends and gradually flattens; above the zero-frequency, the noise gain gradually decreases with increasing frequency. According to... Zero angular frequency .

[0052]

[0053] Convert the angular frequency to the op-amp zero frequency. :

[0054] in, This refers to the capacitance value of either the first or second capacitor. This refers to the resistance value of either the first or second resistor.

[0055] In other words, the op-amp zero frequency It is determined by the first resistor and the first capacitor or the second resistor and the second capacitor, and is independent of other components in the circuit.

[0056] In a capacitor-cross-feedback differential amplifier circuit, the op-amp zero-frequency is higher than the cutoff frequency of the analog differential signal. The cutoff frequency of the analog differential signal is... :

[0057] in, This refers to the capacitance value of either the first or second capacitor. The resistance value of the first or second resistor. This refers to the resistance value of the third or fifth resistor. This is the resistance value of the fourth resistor.

[0058] When the zero-point frequency of the op-amp in the capacitor cross-feedback differential amplifier circuit is greater than the cutoff frequency of the analog differential signal, the op-amp voltage noise transfer function... When the signal is in the falling or concave segment, the noise gain is lower than its low-frequency value, thus suppressing noise. If the zero-point frequency of the op-amp in the capacitor cross-feedback differential amplifier circuit is less than the cutoff frequency of the analog differential signal, the op-amp voltage noise transfer function... If the frequency is still in the low-frequency flat or rising range, the noise gain is close to the low-frequency closed-loop gain, which cannot form effective noise attenuation. The noise of the op-amp input voltage will be amplified to the output terminal, resulting in increased circuit output noise.

[0059] In summary, by connecting the first capacitor between the non-inverting input of the first operational amplifier and the output of the second operational amplifier, and connecting the second capacitor between the non-inverting input of the second operational amplifier and the output of the first operational amplifier, a cross-feedback structure is formed, introducing a noise gain zero-point term into the operational amplifier voltage noise transfer function. By setting the noise gain zero-point term to zero, the operational amplifier zero-point frequency is calculated. Setting the operational amplifier zero-point frequency higher than the cutoff frequency of the analog differential signal suppresses the equivalent input voltage noise of the first and second operational amplifiers, thus improving the output signal-to-noise ratio.

[0060] Example 2 This invention discloses an electronic device comprising an analog differential signal input terminal, an operational amplifier reference voltage source, an ADC differential input terminal, and a capacitor cross-feedback differential amplifier circuit. The positive terminal of the analog differential signal input terminal is connected to one end of a first resistor, and the negative terminal is connected to one end of a second resistor. The positive terminal of the operational amplifier reference voltage source is connected to the power input pins of the first and second operational amplifiers, and the negative terminal is connected to an analog reference ground plane. The positive terminal of the ADC differential input terminal is connected to the differential output positive terminal of the capacitor cross-feedback differential amplifier circuit, and the negative terminal of the ADC differential input terminal is connected to the power input pin of the capacitor cross-feedback differential amplifier circuit.

[0061] The non-inverting input of the first operational amplifier is connected to the first resistor, which is then connected to the output of the second operational amplifier via the first capacitor. The non-inverting input of the second operational amplifier is connected to the second resistor, which is then connected to the output of the first operational amplifier via the second capacitor. The first and second capacitors are interconnected, replacing the traditional ground or interconnect capacitor structure of the input stage of an instrumentation amplifier. This changes the transmission path of internal noise in the first and second operational amplifiers, reducing the total output noise.

[0062] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

Claims

1. A capacitor cross-feedback differential amplifier circuit, characterized in that: The system includes a first operational amplifier, a second operational amplifier, a first capacitor, a second capacitor, and a fourth resistor. The non-inverting input of the first operational amplifier is electrically connected to the positive terminal of the analog differential signal input. One end of the first capacitor is electrically connected to the non-inverting input of the first operational amplifier, and the other end is electrically connected to the output of the second operational amplifier. The non-inverting input of the second operational amplifier is electrically connected to the negative terminal of the analog differential signal input. One end of the second capacitor is electrically connected to the non-inverting input of the second operational amplifier, and the other end is electrically connected to the output of the first operational amplifier. The fourth resistor is positioned between the inverting input of the first operational amplifier and the inverting input of the second operational amplifier.

2. The capacitor cross-feedback differential amplifier circuit according to claim 1, characterized in that: It also includes a third resistor and a fifth resistor. One end of the third resistor is electrically connected to the inverting input terminal of the first operational amplifier, and the other end is electrically connected to the output terminal of the first operational amplifier. One end of the fifth resistor is electrically connected to the inverting input terminal of the second operational amplifier, and the other end is electrically connected to the output terminal of the second operational amplifier.

3. The capacitor cross-feedback differential amplifier circuit according to claim 2, characterized in that: It also includes a first resistor and a second resistor. One end of the first resistor is electrically connected to the positive terminal of the differential signal input, and the other end is electrically connected to the non-inverting input terminal of the first operational amplifier. One end of the second resistor is electrically connected to the analog differential signal, and the other end is electrically connected to the non-inverting input of the second operational amplifier.

4. The capacitor cross-feedback differential amplifier circuit according to claim 3, characterized in that: The first resistor and the second resistor have the same resistance value, the third resistor and the fifth resistor have the same resistance value, and the first capacitor and the second capacitor have the same capacitance value.

5. The capacitor cross-feedback differential amplifier circuit according to claim 1, characterized in that: The operational amplifier zero frequency of the capacitor cross-feedback differential amplifier circuit is greater than the cutoff frequency of the analog differential signal.

6. The capacitor cross-feedback differential amplifier circuit according to claim 5, characterized in that: The op-amp zero frequency of the capacitor cross-feedback differential amplifier circuit is : in, This refers to the capacitance value of either the first or second capacitor. This refers to the resistance value of either the first or second resistor.

7. The capacitor cross-feedback differential amplifier circuit according to claim 5, characterized in that: The cutoff frequency of the analog differential signal is : in, This refers to the capacitance value of either the first or second capacitor. The resistance value of the first or second resistor. This refers to the resistance value of the third or fifth resistor. This is the resistance value of the fourth resistor.

8. The capacitor cross-feedback differential amplifier circuit according to claim 5, characterized in that: The operational amplifier zero-point frequency of the capacitor cross-feedback differential amplifier circuit is calculated based on the operational amplifier voltage noise transfer function, with the noise gain zero term in the operational amplifier voltage noise transfer function set to 0. The operational amplifier voltage noise transfer function is: : in, For DC gain, This refers to the resistance value of the third or fifth resistor. This is the resistance value of the fourth resistor. The resistance value of the first or second resistor. This refers to the capacitance value of either the first or second capacitor. For complex frequencies, This is the zero-point term of the noise gain.

9. The capacitor cross-feedback differential amplifier circuit according to claim 8, characterized in that: The DC gain for: in, This is the resistance value of the third resistor. This is the resistance value of the fourth resistor. This is the resistance value of the fourth resistor.

10. An electronic device, characterized in that, The device includes an analog differential signal input terminal, an operational amplifier reference voltage source, an ADC differential input terminal, and a capacitor cross-feedback differential amplifier circuit as described in any one of claims 1 to 9. The positive terminal of the analog differential signal input terminal is connected to one end of a first resistor, and the negative terminal is connected to one end of a second resistor. The positive terminal of the operational amplifier reference voltage source is connected to the power input pins of the first operational amplifier and the second operational amplifier, and the negative terminal is connected to the analog reference ground plane. The positive terminal of the ADC differential input terminal is connected to the differential output positive terminal of the capacitor cross-feedback differential amplifier circuit, and the negative terminal of the ADC differential input terminal is connected to the power input pin of the capacitor cross-feedback differential amplifier circuit.

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