Chopped wave amplification circuit and electronic equipment

Abstract

The invention discloses a chopping amplification circuit and electronic equipment, and belongs to the technical field of electronic circuits. The chopping amplification circuit comprises a transformer switch amplification module, a differential amplification filtering module and a demodulation module, firstly, an input signal is subjected to first-stage amplification through the transformer switch amplification module, and meanwhile, the input signal is modulated to a high-frequency band far away from low-frequency noise; then, the signal enters a differential amplification filtering module, second-stage amplification is carried out, low-frequency noise is removed, and an inherent high-frequency noise signal subjected to differential amplification and a useful high-frequency signal are output together; and finally, based on the modulation effect of the first-stage amplification, the demodulation module demodulates the useful high-frequency signal and the inherent high-frequency noise signal back to a low-frequency band corresponding to the input signal, and the demodulated signal is fed back and superposed on the input signal to form a closed-loop feedback circuit. Therefore, noise interference caused by differential amplification is reduced, low-frequency noise at the input end of the chopping amplification circuit is reduced, and the measurement precision of the chopping amplification circuit is improved.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a chopper amplifier circuit and electronic device. Background Technology

[0002] A chopper amplifier circuit modulates the target signal to a high frequency band, filters out low-frequency noise, and demodulates it back to the initial frequency, thus achieving low-noise amplification in the low-frequency range. However, the differential amplifier circuit within a chopper amplifier circuit, which performs high-gain amplification of high-frequency AC signals, inherently possesses high-frequency noise. This noise increases the low-frequency noise at the input of the chopper amplifier circuit, thereby affecting its measurement accuracy. Summary of the Invention

[0003] This application provides a chopper amplifier circuit and electronic device that can reduce low-frequency noise at the input of the chopper amplifier circuit, thereby improving the measurement accuracy of the chopper amplifier circuit.

[0004] In a first aspect, embodiments of this application provide a chopper amplifier circuit, the chopper amplifier circuit comprising: The transformer switching amplifier module is used to modulate the input signal and amplify the modulated signal in the first stage. The differential amplifier and filter module is used to amplify the signal output from the transformer switching amplifier module in a second stage, and then perform high-pass filtering on the amplified signal. The demodulation module is used to demodulate the signal output by the differential amplifier and filter module, and then feed the demodulated signal back to the transformer switching amplifier module.

[0005] In some embodiments, the transformer switching amplification module includes: First capacitor; The first transformer and the second transformer, the primary side in-phase terminal of the first transformer and the primary side out-of-phase terminal of the second transformer are used to receive the input signal, the secondary side out-of-phase terminal of the first transformer and the secondary side out-of-phase terminal of the second transformer are grounded through the first capacitor, and the secondary side in-phase terminal of the first transformer and the secondary side in-phase terminal of the second transformer are connected to the differential amplifier and filter module for outputting the modulated and first-stage amplified signal. The first switch and the second switch are connected. The first end of the first switch is connected to the inverting terminal of the primary side of the first transformer. The first end of the second switch is connected to the non-inverting terminal of the primary side of the second transformer. The second ends of the first switch and the second switch are connected to the demodulation module. The control terminals of the first switch and the second switch are used to receive the first control signal and the second control signal, respectively. The first control signal and the second control signal are in an inverted state.

[0006] In some embodiments, the transformer switching amplification module further includes: The first resistor has one end connected to the control terminal of the first switching transistor, and the other end grounded. The second resistor has one end connected to the control terminal of the second switching transistor, and the other end grounded.

[0007] In some embodiments, the frequencies of the first control signal and the second control signal are greater than or equal to And the larger of 100Hz, among which, This indicates the frequency of the input signal.

[0008] In some embodiments, the differential amplification and filtering module includes: The first differential amplifier unit has its first input terminal connected to the in-phase terminal of the secondary side of the first transformer, its second input terminal connected to the in-phase terminal of the secondary side of the second transformer, and its first and second output terminals used to output the signal amplified by the second stage. The first filtering unit has its first input terminal connected to the first output terminal of the first differential amplifier unit, its second input terminal connected to the second output terminal of the first differential amplifier unit, and its first and second output terminals connected to the demodulation module, for outputting the high-pass filtered signal.

[0009] In some embodiments, the differential amplification and filtering module further includes: A buffer unit is connected between the first differential amplifier unit and the first filter unit.

[0010] In some embodiments, the first differential amplification unit includes: The third switch and the fourth switch are connected. The control terminal of the third switch is connected to the in-phase terminal of the secondary side of the first transformer, and the control terminal of the fourth switch is connected to the in-phase terminal of the secondary side of the second transformer. The first terminal of the third switch is connected to the first input terminal of the first filter unit, and the first terminal of the fourth switch is connected to the second input terminal of the first filter unit. The third resistor is connected between the first terminal of the third switching transistor and the power supply. The fourth resistor is connected between the first terminal of the fourth switching transistor and the power supply. The constant current source connects the second terminals of the third and fourth switching transistors to ground.

[0011] In some embodiments, the cutoff frequency range of the first filter unit is [100Hz, f] SW ], where f SW This indicates the frequency of the first control signal.

[0012] In some embodiments, the transformer switching amplification module further includes: The first feedback resistor has one end connected to the second terminal of the first switching transistor and the second terminal of the second switching transistor, and the other end of the first feedback resistor is grounded. The demodulation module includes: The full-bridge switching unit includes a first analog switch, a second analog switch, a third analog switch, and a fourth analog switch. The first terminals of the first and third analog switches are connected to form a first connection node. The first terminals of the second and fourth analog switches are connected to form a second connection node. The first and second connection nodes are connected to a differential amplifier and filter module to receive the signal output by the differential amplifier and filter module. The second differential amplifier unit has its first input terminal connected to the second terminals of the third analog switch and the fourth analog switch, respectively. Its second input terminal is connected to the second terminals of the first analog switch and the second terminals of the second analog switch, respectively. Its output terminal is used to output the demodulated signal. The output feedback unit has its input terminal connected to the output terminal of the second differential amplifier unit. The first output terminal of the output feedback unit is connected to the second terminal of the first switching transistor and the second terminal of the second switching transistor, respectively, and is used to feed the demodulated signal back to the transformer switching amplifier module. The second output terminal of the output feedback unit is used to output the demodulated signal. The first analog switch and the fourth analog switch are controlled by the third control signal, and the second analog switch and the third analog switch are controlled by the fourth control signal. The high-level duration of the first control signal covers the high-level duration of the third control signal, and the high-level duration of the second control signal covers the high-level duration of the fourth control signal.

[0013] In some embodiments, the high-level start time of the third control signal is delayed by t1 time compared to the high-level start time of the first control signal, and the high-level end time of the third control signal is advanced by t2 time compared to the high-level end time of the first control signal. The high-level start time of the fourth control signal is delayed by t3 hours compared to the high-level start time of the second control signal, and the high-level end time of the fourth control signal is advanced by t4 hours compared to the high-level end time of the second control signal. Among them, the durations t1 and t3 are both longer than the turn-on durations of the first and second switching transistors, and the durations t2 and t4 are both longer than the turn-off durations of the first and second switching transistors.

[0014] In some embodiments, the output feedback unit includes: The output resistor is connected at one end to the output terminal of the second differential amplifier unit. The second feedback resistor has one end connected to the other end of the output resistor, and the other end of the second feedback resistor is connected to the second end of the first switching transistor and the second end of the second switching transistor respectively. The second capacitor is connected in parallel across the second feedback resistor.

[0015] In some embodiments, the demodulation module further includes: The second filtering unit is connected between the output of the second differential amplifier unit and the input of the output feedback unit. The cutoff frequency of the second filter unit is greater than or equal to ,in, This indicates the frequency of the input signal.

[0016] Secondly, embodiments of this application also provide an electronic device, the electronic device comprising: The chopper amplifier circuit in the above embodiment.

[0017] Beneficial Effects: This application provides a chopper amplifier circuit, comprising: a transformer switching amplifier module, a differential amplifier filtering module, and a demodulation module. The transformer switching amplifier module modulates the input signal and performs a first-stage amplification on the modulated signal. The differential amplifier filtering module performs a second-stage amplification on the signal output from the transformer switching amplifier module and performs high-pass filtering on the second-stage amplified signal. The demodulation module demodulates the signal output from the differential amplifier filtering module and feeds the demodulated signal back to the transformer switching amplifier module. In this application, firstly, the input signal undergoes a first-stage amplification by the transformer switching amplifier module and is simultaneously modulated to a high-frequency band away from low-frequency noise. Then, the signal enters the differential amplifier filtering module for a second-stage amplification to remove low-frequency noise, and the inherent high-frequency noise signal from the differential amplification is output along with the useful high-frequency signal. Finally, based on the modulation effect of the first-stage amplification, the demodulation module demodulates both the useful high-frequency signal and the inherent high-frequency noise signal back to the low-frequency band corresponding to the input signal. The demodulated signal is then fed back and superimposed on the input signal, forming a closed-loop feedback circuit. Furthermore, the low-frequency noise signal brought by differential amplification will be filtered out in the differential amplification filter module, and the high-frequency noise signal brought by differential amplification will be greatly reduced by the transformer switching amplification module, thereby reducing the interference of noise brought by differential amplification, reducing the low-frequency noise at the input of the chopper amplifier circuit, and thus improving the measurement accuracy of the chopper amplifier circuit. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a chopper amplifier circuit provided in an embodiment of this application; Figure 2A circuit diagram of a chopper amplifier circuit provided for an embodiment of this application; Figure 3 This is a schematic diagram of the waveform corresponding to the control signal in the embodiments of this application.

[0019] Explanation of icon numbers: 100. Transformer switch amplifier module; 200. Differential amplifier and filter module; 210. First differential amplifier unit; 220. First filter unit; 230. Buffer unit; 300. Demodulation module; 310. Full-bridge switching unit; 320. Second differential amplifier unit; 330. Output feedback unit; 340. Second filter unit; C1, First capacitor; T1, First transformer; T2, Second transformer; Q1, First switching transistor; Q2, Second switching transistor; Q3, Third switching transistor; Q4, Fourth switching transistor; R1, First resistor; R2, Second resistor; R3, Third resistor; R4, Fourth resistor; R5, First feedback resistor; S1, First analog switch; S2, Second analog switch; S3, Third analog switch; S4, Fourth analog switch; R6, Output resistor; R7, Second feedback resistor; C2, Second capacitor; I1, Constant current source. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Furthermore, descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0022] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0023] A chopper amplifier circuit modulates the input signal to a high frequency band, filters out low-frequency noise, and demodulates it back to the initial frequency. It is a circuit structure that achieves low-noise amplification in the low-frequency range and can effectively suppress 1 / f noise, a characteristic of traditional amplifier circuits. It is known that chopper amplifier circuits are highly effective in applications where the target signal frequency is in the range of 10Hz or even below 1Hz, such as the precision current source in superconducting cryogenic current comparators and the front-end amplifier for underwater electric field detection.

[0024] However, chopper amplifier circuits have some problems in practical design. For example, during the turn-on and turn-off processes of the transistors in the chopper amplifier circuit, the injected charge and clock feedthrough introduce switching charge noise corresponding to the switching frequency. This noise is amplified along with the input signal and ultimately superimposed on the output signal. Furthermore, whether it's a differential amplifier circuit built with transistors or an ultra-low noise operational amplifier integrated circuit, their high-frequency noise is generally in the nV range. Therefore, the low-frequency noise at the input of the chopper amplifier circuit built on this basis will be slightly greater than the high-frequency noise of the aforementioned amplifier circuits. This leads to an increase in low-frequency noise at the input of the chopper amplifier circuit, thus affecting the measurement accuracy of the chopper amplifier circuit. Therefore, it is difficult to achieve a noise level of 1nV or even lower at 1Hz.

[0025] Please see Figure 1 As shown, Figure 1 This is a schematic diagram of a chopper amplifier circuit provided in an embodiment of this application.

[0026] This application provides a chopper amplifier circuit, which includes a transformer switching amplifier module 100, a differential amplifier and filter module 200, and a demodulation module 300. The transformer switching amplifier module 100 is used to modulate the input signal and amplify the modulated signal in a first stage. The differential amplifier and filter module 200 is used to amplify the signal output by the transformer switching amplifier module 100 in a second stage and perform high-pass filtering on the amplified signal. The demodulation module 300 is used to demodulate the signal output by the differential amplifier and filter module 200 and feed the demodulated signal back to the transformer switching amplifier module 100.

[0027] It is important to understand that a chopper amplifier circuit modulates an input low-frequency signal to a high-frequency band, then amplifies and demodulates it to recover the original signal. It can be used in fields such as sensor signal processing and medical electronics. The input signal in this application can be a differential voltage signal or a single-ended voltage signal. For example, the output signal of an electric field sensor in the field of electric field detection.

[0028] The transformer switching amplifier module 100 modulates the input signal and performs a first-stage amplification on the modulated signal. In other words, the transformer switching amplifier module 100 mixes the input signal with a high-frequency switching signal, converting it into a high-frequency signal, while simultaneously using a transformer to achieve the first-stage amplification. This allows the output signal of the transformer switching amplifier module 100 to be far removed from the 1 / f noise frequency, thus facilitating significant attenuation of the 1 / f noise in subsequent stages without affecting the amplitude of the modulated signal.

[0029] The differential amplifier and filter module 200 is used to amplify the signal output from the transformer switching amplifier module 100 in a second stage, and then perform high-pass filtering on the amplified signal. In other words, the differential amplifier and filter module 200 suppresses common-mode noise, improves the signal-to-noise ratio, and filters out low-frequency interference in the signal, such as 1 / f noise, while retaining the target frequency band signal. Thus, the effect of the differential amplifier and filter module 200 on signal noise is limited to the inherent high-frequency noise. The high-frequency noise of the differential amplifier and filter module 200 can reach several nV (nanovolts), and therefore, when the high-frequency noise is equivalent to the input of the chopper amplifier circuit, it will reduce the amplification factor corresponding to the first stage, meaning the equivalent high-frequency noise at the input may be less than 1 nV.

[0030] It should be noted that the amplification factor of the differential amplifier and filter module 200 is usually very large, which can be greater than 100 times, in order to ensure a large open-loop gain of the differential amplifier and filter module 200.

[0031] The demodulation module 300 demodulates the signal output by the differential amplifier and filter module 200 and feeds the demodulated signal back to the transformer switching amplifier module 100. In other words, the demodulation module 300 demodulates the signal back to its initial state, restoring the high-frequency signal output by the differential amplifier and filter module 200 to the low-frequency signal corresponding to the input signal. Simultaneously, the demodulated signal is fed back to the preceding transformer switching amplifier module 100, forming a closed-loop control to stabilize circuit performance.

[0032] Through the above technical solution, in this application, firstly, the input signal undergoes first-stage amplification via the transformer switching amplification module 100, and is simultaneously modulated to a high-frequency band far removed from low-frequency noise. Then, the signal enters the differential amplification and filtering module 200 for second-stage amplification and removal of low-frequency noise. The inherent high-frequency noise signal from the differential amplification is output along with the useful high-frequency signal. Finally, based on the modulation effect of the first-stage amplification, the demodulation module 300 demodulates both the useful high-frequency signal and the inherent high-frequency noise signal back to the low-frequency band corresponding to the input signal. The demodulated signal is then superimposed on the input signal, forming a closed-loop feedback circuit. Consequently, the low-frequency noise signal from the differential amplification is filtered out in the differential amplification and filtering module, and the high-frequency noise signal from the differential amplification is significantly reduced due to the transformer switching amplification module. This reduces the interference from the noise from the differential amplification, decreases the low-frequency noise at the input of the chopper amplifier circuit, and thus improves the measurement accuracy of the chopper amplifier circuit.

[0033] Please see Figure 2 As shown, Figure 2 This is a circuit diagram of a chopper amplifier circuit provided in an embodiment of this application.

[0034] In some embodiments, the transformer switching amplification module 100 includes: a first capacitor C1, a first transformer T1, a second transformer T2, a first switch Q1, and a second switch Q2. The primary side in-phase terminal of the first transformer T1 and the primary side out-of-phase terminal of the second transformer T2 are used to receive input signals. The secondary side out-of-phase terminal of the first transformer T1 and the secondary side out-of-phase terminal of the second transformer T2 are grounded through the first capacitor C1. The secondary side in-phase terminal of the first transformer T1 and the secondary side in-phase terminal of the second transformer T2 are connected to the differential amplification and filtering module 200 for outputting the modulated and first-stage amplified signal. The first terminal of the first switch Q1 is connected to the primary side out-of-phase terminal of the first transformer T1, the first terminal of the second switch Q2 is connected to the primary side in-phase terminal of the second transformer T2, the second terminal of the first switch Q1 is connected to the second terminal of the second switch Q2, and is connected to the demodulation module 300. The control terminals of the first switch Q1 and the second switch Q2 are used to receive a first control signal and a second control signal, respectively. The first control signal and the second control signal are in an out-of-phase state.

[0035] Specifically, the first switch Q1 and the second switch Q2 can be MOSFETs. The gate of the MOSFET serves as the control terminal of both switches Q1 and Q2, the drain of the MOSFET serves as the first terminal of both switches Q1 and Q2, and the source of the MOSFET serves as the second terminal of both switches Q1 and Q2. The first transformer T1 and the second transformer T2 have the same turns ratio, with a primary-to-secondary turns ratio of less than 1:100. Furthermore, the positive input terminal Uin+ of the input signal is connected to the non-inverting input terminal of the primary winding of the first transformer T1, and the negative input terminal Uin- is connected to the inverting input terminal of the primary winding of the second transformer T2. The inverting terminal of the primary winding of the first transformer T1 is connected to the drain of the first switch Q1, and the non-inverting terminal of the primary winding of the second transformer T2 is connected to the drain of the second switch Q2. The inverting terminals of the secondary windings of the first transformer T1 and the second transformer T2 are grounded through the first capacitor C1, which serves as a compensation capacitor. The sources of both switches Q1 and Q2 are connected to the demodulation module 300. The gates of the first switch Q1 and the second switch Q2 receive the first control signal and the second control signal, respectively. The first switch Q1 and the second switch Q2 change their on / off states under the control of the corresponding first control signal and the second control signal. Thus, by controlling the on / off state of the first switch Q1 and the second switch Q2 based on the first control signal and the second control signal, the input signal can be mixed with the high-frequency switching signal and converted into a high-frequency signal. This makes the signal output by the transformer switching amplifier module 100 far away from the 1 / f noise frequency, and thus the transformer is used to realize the first stage of signal amplification.

[0036] In some examples, the transformer switching amplifier module 100 further includes resistors R8 and R9. The gate of the first switching transistor Q1 is connected to a first control signal via resistor R8, and the gate of the second switching transistor Q2 is connected to a second control signal via resistor R9. Resistors R8 and R9 thus limit the input current of the first switching transistor Q1 and the second switching transistor Q2, protecting the transistors from damage due to excessive current and ensuring stable circuit operation.

[0037] Please see Figure 3 As shown, Figure 3 This is a schematic diagram of the waveform corresponding to the control signal in the embodiments of this application.

[0038] In this embodiment, the first control signal SW1 and the second control signal SW2 are square wave signals. The fact that the first and second control signals are in opposite phases indicates that they are complementary in time; that is, when the square wave of the first control signal is high, the square wave of the second control signal is low, and vice versa. In this embodiment, the conduction of the first switch Q1 and the second switch Q2 is controlled by a high level, and the turn-off of the first switch Q1 and the second switch Q2 is controlled by a low level.

[0039] It should be noted that when the input signal is a differential signal, the positive input terminal Uin+ and the negative input terminal Uin- are connected to the positive and negative phase signals of the signal, respectively. When the input signal is a single-ended signal, the positive input terminal Uin+ receives the actual signal input, and the negative input terminal Uin- is usually grounded or connected to a fixed reference voltage.

[0040] It should also be noted that the first switching transistor Q1 and the second switching transistor Q2 can also be switching transistors with switching functions, such as transistors, IGBTs, or JEFTs.

[0041] Understandably, this application uses the first switch Q1 and the second switch Q2, under the control of corresponding first and second control signals, to modulate the input signal into a high-frequency signal, while simultaneously utilizing a transformer to achieve the first stage of signal amplification. This ensures that the signal output from the transformer-controlled switching amplification module 100 is far removed from the 1 / f noise frequency, facilitating significant attenuation of the 1 / f noise in subsequent stages without affecting the amplitude of the modulated signal. The modulated high-frequency signal is then amplified by the first transformer T1 and the second transformer T2, making the subsequent high-frequency signal equivalent to the input of the chopper amplifier circuit. This reduces the amplification factor corresponding to the first stage, thereby reducing interference from the differential amplification and decreasing low-frequency noise at the input of the chopper amplifier circuit.

[0042] Please continue reading. Figure 2 As shown, in some embodiments, the transformer switching amplification module 100 further includes: a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the control terminal of the first switching transistor Q1, and the other end of the first resistor R1 is grounded; one end of the second resistor R2 is connected to the control terminal of the second switching transistor Q2, and the other end of the second resistor R2 is grounded.

[0043] Understandably, the transformer switching amplifier module 100 is grounded through the first resistor R1 and the second resistor R2, which ensures that the first switch Q1 and the second switch Q2 are in the off state by default, thus ensuring that they remain in the off state when there is no input signal and preventing false turn-on.

[0044] In some embodiments, the frequencies of the first control signal and the second control signal are greater than or equal to And the larger of 100Hz, among which, This indicates the frequency of the input signal.

[0045] Understandably, if the input signal frequency range is 0Hz to fsig and the 1 / f noise frequency range is 0Hz to 10Hz, then the frequencies of the first and second control signals must be greater than or equal to... The larger of 100Hz and 100Hz ensures that the frequency band of the modulated input signal is far from the 1 / f noise band. This facilitates significant attenuation of 1 / f noise in subsequent stages without affecting the amplitude of the modulated signal.

[0046] Please continue reading. Figure 2 As shown, in some embodiments, the differential amplifier and filter module 200 includes: a first differential amplifier unit 210 and a first filter unit 220. The first input terminal of the first differential amplifier unit 210 is connected to the non-inverting terminal of the secondary side of the first transformer T1, and the second input terminal of the first differential amplifier unit 210 is connected to the non-inverting terminal of the secondary side of the second transformer T2. The first output terminal and the second output terminal of the first differential amplifier unit 210 are used to output the signal amplified by the second stage. The first input terminal of the first filter unit 220 is connected to the first output terminal of the first differential amplifier unit 210, and the second input terminal of the first filter unit 220 is connected to the second output terminal of the first differential amplifier unit 210. The first output terminal and the second output terminal of the first filter unit 220 are connected to the demodulation module 300 and are used to output the signal after high-pass filtering.

[0047] It is important to understand that when the differential amplifier and filter module 200 amplifies the signal, it introduces noise, which includes both 1 / f noise and high-frequency noise. The first filter unit 220 can be a high-pass filter circuit or device. The first differential amplifier unit 210 suppresses common-mode noise and increases signal gain through differential amplification. The first filter unit 220 is connected to the differential output terminal of the first differential amplifier unit 210 and is used to filter out low-frequency noise in the modulated signal. This low-frequency noise includes 1 / f noise introduced by differential amplification and low-frequency noise introduced by the transformer switching amplifier module 100. It is known that the input signal has already had its modulated signal frequency band moved away from the 1 / f noise frequency band in the transformer switching amplifier module 100. Therefore, the first filter unit 220 can significantly attenuate the 1 / f noise and other low-frequency noise introduced by differential amplification without affecting the amplitude of the modulated signal.

[0048] In some embodiments, the differential amplification and filtering module 200 further includes a buffer unit 230, which is connected between the first differential amplification unit 210 and the first filtering unit 220.

[0049] Specifically, the first input terminal of the buffer unit 230 is connected to the first output terminal of the first differential amplifier unit 210, the second input terminal of the buffer unit 230 is connected to the second output terminal of the first differential amplifier unit 210, the first output terminal of the buffer unit 230 is connected to the first input terminal of the first filter unit 220, and the second output terminal of the buffer unit 230 is connected to the second input terminal of the first filter unit 220.

[0050] Understandably, in this embodiment of the application, the buffer unit 230 achieves impedance conversion and isolation of the signal without changing the signal amplitude and phase, ensuring that the amplitude and phase of the amplified signal are not distorted, and providing an accurate signal source for the subsequent filtering and demodulation process.

[0051] In some embodiments, the first differential amplifier unit 210 includes: a third switch Q3, a fourth switch Q4, a third resistor R3, a fourth resistor R4, and a constant current source I1. The control terminal of the third switch Q3 is connected to the non-inverting terminal of the secondary side of the first transformer T1, and the control terminal of the fourth switch Q4 is connected to the non-inverting terminal of the secondary side of the second transformer T2. The first terminal of the third switch Q3 is connected to the first input terminal of the first filter unit 220, and the first terminal of the fourth switch Q4 is connected to the second input terminal of the first filter unit 220. The third resistor R3 is connected between the first terminal of the third switch Q3 and the power supply. The fourth resistor R4 is connected between the first terminal of the fourth switch Q4 and the power supply. The second terminals of the third switch Q3 and the second terminals of the fourth switch Q4 are grounded through the constant current source I1. The power supply is configured according to the specific implementation scheme; for example, the power supply can be 2V to 12V or 12V to 36V.

[0052] The buffer unit 230 can adopt a follower structure. The buffer unit 230 includes operational amplifier U1 and operational amplifier U2. The non-inverting input terminal of operational amplifier U1 is connected to the first terminal of the third switch Q3. The output terminal of operational amplifier U1 is connected to the inverting input terminal of operational amplifier U1 and the first input terminal of the first filter unit 220. The non-inverting input terminal of operational amplifier U2 is connected to the first terminal of the fourth switch Q4. The output terminal of operational amplifier U2 is connected to the inverting input terminal of operational amplifier U2 and the second input terminal of the first filter unit 220.

[0053] The first filtering unit 220 may include resistors R10 and R11, capacitors C3 and C4. One end of resistor R10 is connected to the output terminal of operational amplifier U1, and the other end of resistor R10 is connected to one end of capacitor C3. One end of resistor R11 is connected to the output terminal of operational amplifier U2, and the other end of resistor R11 is connected to one end of capacitor C4. The other ends of capacitors C3 and C4 are connected to demodulation module 300 for outputting the high-pass filtered signal.

[0054] Specifically, the third switch Q3 and the fourth switch Q4 in the first differential amplifier unit 210 can be JFETs. The gate of the JFET serves as the control terminal of the third switch Q3 and the fourth switch Q4, the drain of the JFET serves as the first terminal of the third switch Q3 and the fourth switch Q4, and the source of the JFET serves as the second terminal of the third switch Q3 and the fourth switch Q4. The first differential amplifier unit 210 includes the first differential amplifier unit 210 composed of the third switch and the fourth switch Q4, and subsequent buffer units 230, first filter units 220, etc. The inverting terminal of the amplitude winding of the first transformer T1 and the inverting terminal of the amplitude winding of the second transformer T2 are connected and grounded through the first capacitor C1. The inverting terminal of the amplitude winding of the first transformer T1 and the non-inverting terminal of the amplitude winding of the second transformer T2 are respectively connected to the gates of the third switch Q3 and the fourth switch Q4. The sources of the third switch Q3 and the fourth switch Q4 are grounded through a constant current source I1 circuit, achieving high amplification and high common-mode rejection ratio in the differential amplifier circuit. The drains of the third switch Q3 and the fourth switch Q4 are connected to the non-inverting inputs of operational amplifiers U1 and U2, respectively, as the outputs of the differential amplifier circuit. The outputs of operational amplifiers U1 and U2 are connected to resistors R10 and R11, respectively. Resistors R10 and R11, capacitors C3 and C4 can form a high-pass filter to filter out low-frequency noise from the transformer switching module and the first differential amplifier unit 210.

[0055] The first and second stage amplification processes are as follows: When the first switch Q1 is turned on, the second switch Q2 is turned off. The input terminal Uin+ is amplified by the first transformer T1 and then enters the third switch Q3. The capacitance of the first capacitor C1 is very large, resulting in a very low equivalent impedance at the switching frequency. Therefore, the control terminal of the fourth switch Q4 is equivalent to being grounded. The overall equivalent is that the input terminal Uin+ undergoes two-stage amplification through the transformer and the first differential amplifier unit 210. Similarly, when the first switch Q1 is turned off, the second switch Q2 is turned on. The input terminal Uin- is amplified by the second transformer T2 and then enters the fourth switch Q4. The capacitance of the first capacitor C1 is very large, resulting in a very low equivalent impedance at the switching frequency. Therefore, the control terminal of the third switch Q3 is equivalent to being grounded. The overall equivalent is that the input terminal Uin- undergoes two-stage amplification through the transformer and the first differential amplifier unit 210.

[0056] The constant current source I1, ranging from 1mA to 2mA, provides a stable current source to the sources of the differential pair. Constant current source I1 ensures that the equivalent source impedance of the third switch Q3 and the fourth switch Q4 is zero. Ideally, the gain of the differential amplifier circuit can reach the maximum amplification factor of the third switch Q3. Furthermore, constant current source I1 ensures that when a common-mode signal is input, the source impedance of the third switch Q3 and the fourth switch Q4 is extremely high, resulting in a very small common-mode signal amplification factor. When a differential-mode signal is input, the differential-mode current of the third switch Q3 and the fourth switch Q4 does not enter constant current source I1, resulting in an infinitesimal equivalent source impedance and a very large differential-mode signal amplification factor, thus achieving a high common-mode rejection ratio.

[0057] It should be noted that the third switch Q3 and the fourth switch Q4 can also be switching transistors with switching functions, such as MOSFETs, bipolar transistors or IGBTs.

[0058] Understandably, in this application, the turns ratio of the primary winding of the first transformer T1 and the second transformer T2 is n. After the input signal is modulated by the first switch Q1 and the second switch Q2, it enters the primary winding of the transformer for signal amplification and is output to the first differential amplifier unit 210 in the differential amplifier and filter module 200 through the amplitude winding of the transformer. The frequency band of the modulated input signal is synchronized with the switching frequencies of the third switch and the fourth switch Q4, and is far from the 1 / f noise frequency. Therefore, the high-pass filter in the subsequent stage can significantly attenuate the 1 / f noise brought by the differential amplification without affecting the amplitude of the modulated signal. In this way, the influence of the first differential amplifier unit 210 on the signal noise is only high-frequency noise. The high-frequency noise of the differential amplifier circuit can be several nV. The high-frequency noise equivalent to the primary winding of the transformer, that is, the input end of the signal, will be reduced by a factor of n. Therefore, the high-frequency noise equivalent to the input end may be less than 1nV.

[0059] In some embodiments, the cutoff frequency range of the first filter unit 220 is [100Hz, f] SW ], where f SW This indicates the frequency of the first control signal.

[0060] Understandably, the cutoff frequency range of the first filter unit 220 is [100Hz, f]. SW That is, the first filter unit 220 will filter out low-frequency noise less than 100Hz, and through the cutoff frequency range of the first filter unit 220, the 1 / f noise introduced by the differential amplifier circuit can be fully filtered out.

[0061] Please continue reading. Figure 2 As shown, in some embodiments, the transformer switching amplification module 100 further includes: a first feedback resistor R5, one end of the first feedback resistor R5 is connected to the second end of the first switching transistor Q1 and the second end of the second switching transistor Q2 respectively, and the other end of the first feedback resistor R5 is grounded. The demodulation module 300 includes a full-bridge switching unit 310, a second differential amplifier unit 320, and an output feedback unit 330. The full-bridge switching unit 310 includes a first analog switch S1, a second analog switch S2, a third analog switch S3, and a fourth analog switch S4. The first terminals of the first analog switch S1 and the third analog switch S3 are connected to form a first connection node. The first terminals of the second analog switch S2 and the fourth analog switch S4 are connected to form a second connection node. The first and second connection nodes are connected to the differential amplifier and filter module 200 to receive the signal output by the differential amplifier and filter module 200. The first input terminal of the second differential amplifier unit 320 is connected to the second terminals of the third analog switch S3 and the fourth analog switch S4, respectively. The second input terminal of the second differential amplifier unit 320 is connected to the first terminal of the first analog switch S1. The second terminal of the second analog switch S2 is connected to the second terminal of the second analog switch S2. The output terminal of the second differential amplifier unit 320 is used to output the demodulated signal. The input terminal of the output feedback unit 330 is connected to the output terminal of the second differential amplifier unit 320. The first output terminal of the output feedback unit 330 is connected to the second terminal of the first switch Q1 and the second terminal of the second switch Q2, respectively, and is used to feed the demodulated signal back to the transformer switch amplifier module 100. The second output terminal of the output feedback unit 330 is used to output the demodulated signal. Among them, the first analog switch S1 and the fourth analog switch S4 are controlled by the third control signal, and the second analog switch S2 and the third analog switch S3 are controlled by the fourth control signal. The high-level duration of the first control signal covers the high-level duration of the third control signal, and the high-level duration of the second control signal covers the high-level duration of the fourth control signal.

[0062] It should be understood that the first feedback resistor R5 in the transformer switching amplifier module 100 is used for signal feedback.

[0063] The full-bridge switching unit 310 in the demodulation module 300 is used to receive the signal output by the differential amplification and filtering module 200. Specifically, the first connection node between the first terminal of the first analog switch S1 and the first terminal of the third analog switch S3 is connected to the first output terminal Uin2+ of the first filtering unit 220, and the second connection node between the first terminal of the second analog switch S2 and the first terminal of the fourth analog switch S4 is connected to the second output terminal Uin2- of the first filtering unit 220. The first analog switch S1 and the fourth analog switch S4 are controlled by a third control signal, and the second analog switch S2 and the third analog switch S3 are controlled by a fourth control signal. The high-level duration of the first control signal covers the high-level duration of the third control signal, and the high-level duration of the second control signal covers the high-level duration of the fourth control signal. This means that during the period when the first control signal SW1 controls the first switch Q1 to conduct, the third control signal SW3 controls the first analog switch S1 and the fourth analog switch S4 to conduct, and the first analog switch S1 and... The conduction time of the fourth analog switch S4 is no greater than the conduction time of the first switch Q1. Similarly, during the period when the second control signal SW2 controls the second switch Q2 to conduct, the fourth control signal SW4 controls the second analog switch S2 and the third analog switch S3 to conduct, and the conduction time of the second analog switch S2 and the third analog switch S3 is no greater than the conduction time of the second switch Q2. This makes the modulation logic of the full-bridge switching unit 310 and the front-stage transformer switching amplification module 100 match, that is, the signal polarity during demodulation is consistent with that during modulation, so as to ensure that the demodulation can accurately restore the signal.

[0064] The second output terminal of the output feedback unit 330 is used to output the demodulated signal. The first output terminal of the output feedback unit 330 is connected to the second terminal of the first switch Q1 and the second terminal of the second switch Q2 respectively. The feedback facilitates the control of the amplification factor of the chopper amplifier circuit.

[0065] For example, the analog switches in the full-bridge switching unit 310 may be, but are not limited to, switching transistors with switching functions such as CMOS transistors, MOS transistors, triodes, IGBT transistors or JEFT transistors.

[0066] Please see Figure 3As shown, it's important to understand that a MOSFET has a turn-on rise time, a turn-on delay time, a turn-off fall time, and a turn-off delay time. Therefore, when a MOSFET is turned on, there is a turn-on time (turn-on rise time + turn-on delay time), and when it is turned off, there is a turn-off time (turn-off fall time + turn-off delay time). This introduces switching noise during both turn-on and turn-off, with an amplitude within 100nV. The switching noise introduced by the first switch Q1 and the second switch Q2 is further amplified by the differential amplifier of the transformer and the JFET. The amplified switching noise time-domain waveform is shown below. Figure 3 As shown, when the first switch Q1 is turned on and the second switch Q2 is turned off, a positive pulse signal will be generated. When the first switch Q1 is turned off and the second switch Q2 is turned on, a negative pulse signal will be generated. This introduces switching charge noise corresponding to the switching frequency, which will be amplified together with the input signal and finally superimposed on the output signal, affecting the detection accuracy of the chopper amplifier circuit.

[0067] In some embodiments, the high-level start time of the third control signal is delayed by t1 time compared to the high-level start time of the first control signal, and the high-level end time of the third control signal is advanced by t2 time compared to the high-level end time of the first control signal; the high-level start time of the fourth control signal is delayed by t3 time compared to the high-level start time of the second control signal, and the high-level end time of the fourth control signal is advanced by t4 time compared to the high-level end time of the second control signal; wherein, the durations t1 and t3 are both greater than the turn-on durations of the first switch Q1 and the second switch Q2, and the durations t2 and t4 are both greater than the turn-off durations of the first switch Q1 and the second switch Q2.

[0068] For example, the switching timing of the first control signal to the fourth control signal is as follows: Figure 3As shown, the first control signal SW1 and the second control signal SW2 are in an inverted state, with a high-level duty cycle of 50% for both. The start time of the high level of the third control signal SW3 is t1 time later than the start time of the corresponding high level in the first control signal SW1, and the end time of the high level of the third control signal SW3 is t2 time earlier than the end time of the corresponding high level in the first control signal SW1. After the first control signal sends a high level to the first switch Q1, and after t1 time, the third control signal sends a high level to the corresponding analog switch. After the third control signal sends a low level to the corresponding analog switch, and after t2 time... The first control signal sends a low level to the first switch Q1. Similarly, the start time of the high level of the fourth control signal SW4 is t3 seconds later than the start time of the corresponding high level in the second control signal SW2, and the end time of the high level of the fourth control signal SW4 is t4 seconds earlier than the end time of the corresponding high level in the second control signal SW2. Therefore, after the second control signal sends a high level to the second switch Q2, after t3 seconds, the fourth control signal sends a high level to the corresponding analog switch. After the fourth control signal sends a low level to the corresponding analog switch, after t4 seconds, the second control signal sends a low level to the second switch Q2. The duration of the high level of the first control signal corresponds to the duration of the high level of the third control signal, and the duration of the high level of the second control signal corresponds to the duration of the high level of the fourth control signal. Therefore, the duration of the high level of the third control signal is less than the duration of the corresponding high level of the first control signal, and the duration of the high level of the fourth control signal is less than the duration of the high level of the second control signal.

[0069] It should be noted that the turn-on duration is the total duration including the turn-on rise time and turn-on delay time, and the turn-off duration is the total duration including the turn-off rise time and turn-off delay time. The durations t1, t2, t3, and t4 can be the same or different, as long as they are sufficient to prevent switching noise from being transmitted to the output.

[0070] Understandably, the first control signal SW1 and the second control signal SW2 will generate charge injection and clock feedthrough phenomena at the start and end times of their high-level states, respectively, introducing switching noise. Since the first control signal SW1 and the second control signal SW2 are present in the transformer switching circuit, the switching noise signal will be amplified along with the input signal. This application addresses this by creating a time difference between the third and fourth control signals and the first and second control signals. During this time difference, the analog switches in the full-bridge switching unit 310 are all in the open state, preventing the input signal from being transmitted to the output. Therefore, the switching noise introduced by the first control signal SW1 and the second control signal SW2 cannot be transmitted to the output. This solves the switching noise problem introduced by the first switching transistor Q1 and the second switching transistor Q2, thereby improving the detection accuracy of the chopper amplifier circuit.

[0071] It should be noted that in the chopper amplifier circuit of this application, during the time difference between the third control signal, the fourth control signal and the first control signal and the second control signal, the waveforms output by the first analog switch S1 to the fourth analog switch S4 are equal to 0 during the time difference. Therefore, the output signal of the chopper amplifier circuit will be distorted compared with the input signal. The demodulation module 300 of this application uses the characteristic of amplifier negative feedback to improve signal linearity and compensate for the distortion of the output signal.

[0072] Please see Figure 2 As shown, in some embodiments, the second differential amplifier unit 320 includes an operational amplifier U3, resistors R12, R13, R14, and R15. One end of resistor R12 is connected to the second terminals of the third analog switch S3 and the fourth analog switch S4, respectively. One end of resistor R13 is connected to the second terminals of the first analog switch S1 and the second analog switch S2, respectively. The other end of resistor R12 is connected to the inverting input terminal of operational amplifier U3, and the other end of resistor R13 is connected to the non-inverting input terminal of operational amplifier U3. One end of resistor R15 is connected to the non-inverting input terminal of operational amplifier U3, and the other end of resistor R15 is grounded. One end of resistor R14 is connected to the inverting input terminal of operational amplifier U3, and the other end of resistor R14 is connected to the output terminal of operational amplifier U3. The output terminal of operational amplifier U3 is connected to the output feedback unit 330. Wherein, the resistance values ​​of resistors R12, R13, R14, and R15 are equal, such that the ratio of the output to the input of the second differential amplifier unit 320 is equal to 1.

[0073] Understandably, since the ratio of the output to the input of the second differential amplifier unit 320 is equal to 1, there is no signal amplification process during the time it takes for the signal to pass through the full-bridge switching unit 310 and the second differential amplifier unit 320 to the circuit output. Therefore, the switching noise introduced by the third and fourth control signals is much lower than the amplitude of the amplified input signal. Furthermore, the opening and closing times of the third and fourth control signals are asynchronous. Even with the same durations t1, t2, t3, and t4, there is a time difference of 2t, so there is no noise accumulation caused by the synchronous opening and closing of the switches. Therefore, the switching noise of the third and fourth control signals has a negligible impact on the output signal. In addition, because the chopper amplifier circuit of this application has a negative feedback structure in the demodulation module 300, it can compensate for the attenuation of the input signal amplitude caused by the 2t time difference, automatically compensate for signal loss within the time difference, increase the linearity of the chopper amplifier circuit, and achieve precise amplification factor control and suppression of switching charge.

[0074] Please see Figure 2As shown, in some embodiments, the output feedback unit 330 includes: an output resistor R6, a second feedback resistor R7, and a second capacitor C2. One end of the output resistor R6 is connected to the output terminal of the second differential amplifier unit 320; one end of the second feedback resistor R7 is connected to the other end of the output resistor R6, and the other end of the second feedback resistor R7 is connected to the second terminal of the first switch Q1 and the second terminal of the second switch Q2, respectively; the second capacitor C2 is connected in parallel across the second feedback resistor R7.

[0075] It's important to understand that the node between the output resistor R6 and the second feedback resistor R7 is the output terminal of the chopper amplifier circuit. The amplification factor of the chopper amplifier circuit is... Since the impedance of resistor R1 is very small, typically 1Ω, and assuming the amplification factor is 1000 times, R7 = 999Ω, adjusting R11 is easier than adjusting R1. Therefore, the amplification factor of the chopper amplifier circuit can be freely changed by adjusting R11.

[0076] Please see Figure 2 As shown, in some embodiments, the demodulation module 300 further includes a second filtering unit 340, which is connected between the output of the second differential amplifier unit 320 and the input of the output feedback unit 330; wherein the cutoff frequency of the second filtering unit 340 is greater than that of the second differential amplifier unit 320. or equal to ,in, This indicates the frequency of the input signal.

[0077] For example, the second filter unit 340 includes an operational amplifier U4, resistors R16, R17, and R18, and capacitors C5 and C6. One end of resistor R16 is connected to the output terminal of the second differential amplifier unit 320, and the other end of resistor R16 is connected to one end of resistor R17, one end of capacitor C5, and one end of resistor R18, respectively. The other end of capacitor C5 is grounded. The other end of resistor R17 is connected to the output terminal of operational amplifier U4, and the other end of resistor R18 is connected to the inverting input terminal of operational amplifier U4. The non-inverting input terminal of operational amplifier U4 is grounded. One end of capacitor C6 is connected to the inverting input terminal of operational amplifier U4, and the other end of capacitor C6 is connected to the output terminal of operational amplifier U4. The output terminal of operational amplifier U4 is connected to the input terminal of output feedback unit 330. The second filter unit 340 constitutes a low-pass filter.

[0078] In some examples, the frequencies of the first control signal, the second control signal, the third control signal, and the fourth control signal are all greater than or equal to [the specified frequency]. The larger of 100Hz and 100Hz.

[0079] It is known that the cutoff frequency of the second filter unit 340 is greater than or equal to the frequency of the input signal, thus the second filter unit 340 can effectively filter out noise outside the bandwidth of the input signal. Furthermore, when the analog switch uses CMOS, switching noise is also introduced, but it is not amplified at the output of the chopper amplifier circuit. If the amplification factor of the chopper amplifier circuit is A, the noise amplitude introduced by the analog switch is n. s Then the amplitude of the analog switching noise equivalent to the input of the chopper amplifier circuit is n. s / A,A is generally greater than 100. At the same time, the frequency of the switching noise is the same as the frequency of the switching signal control. Outside the signal bandwidth, the switching noise will be greatly attenuated after low-pass filtering. Therefore, the influence of analog switching noise on the equivalent input noise of the chopper amplifier circuit can be greatly reduced.

[0080] The equivalent noise effect of this application will be illustrated below through the following examples: In the first example, the chopper amplifier circuit constructed according to this application has a chopper amplifier factor of 1000 times, a transformer amplification factor of 10 times, and time durations t1, t2, t3, and t4 are all the same (t). The measured equivalent input voltage noise at 1Hz is... After removing the transformer, the circuit amplification factor is 1000 times. The durations t1, t2, t3, and t4 are all the same (t). The measured equivalent input voltage noise at 1Hz is... .

[0081] The second example is a chopper amplifier circuit built according to this application. The chopper amplifier circuit has a gain of 1000 times, the transformer has a gain of 10 times, the switching frequency is 300Hz, there is no delay time, and the equivalent input voltage noise at 1Hz is... The switching delay time t = 10µs, and the equivalent input voltage noise at 1Hz is: .

[0082] The third example is a chopper amplifier circuit built according to this application. The chopper amplifier circuit has a gain of 1000 times, the transformer has a gain of 10 times, the switching frequency is 300Hz, the delay time is t=10us, and the equivalent input voltage noise at 1Hz is... ; Fourth example: A chopper amplifier circuit constructed according to this application has a gain of 1000, no transformer, a switching frequency of 300Hz, a delay time of t=10µs, and an equivalent input voltage noise at 1Hz. ; Fifth example: A chopper amplifier circuit built according to this application has a chopper amplifier factor of 1000, a transformer amplification factor of 10, a switching frequency of 300Hz, no delay time, and an equivalent input voltage noise at 1Hz. .

[0083] In summary, this application provides a chopper amplifier circuit. Due to the presence of the transformer, it can achieve a first-stage amplification of the signal before the input signal is amplified by the differential amplifier circuit. Assuming the transformer's amplification factor is 10, and the high-frequency noise of the differential amplifier circuit is... Then, the high-frequency noise of the differential amplifier circuit, when equivalent to the noise at the input of the chopper amplifier circuit, becomes... This reduces the impact of noise from the subsequent amplifier stage on the equivalent input noise of the chopper amplifier circuit, thus achieving an equivalent input noise below 1nV / √Hz. This reduces high-frequency signal interference from the differential amplifier, decreases low-frequency noise at the chopper amplifier circuit input, and ultimately improves the measurement accuracy of the chopper amplifier circuit.

[0084] In addition, by adjusting the switching time in the demodulation module 300, this application can shield the noise from charge injection and clock feedthrough generated during the modulation process, thereby solving the switching noise problem introduced by the first switch Q1 and the second switch Q2, and thus improving the detection accuracy of the chopper amplifier circuit.

[0085] This application also provides an electronic device, which includes a chopper amplifier circuit as described in the above embodiments.

[0086] For example, electronic devices could be precision current sources in superconducting cryogenic current comparators and front-end amplifiers for underwater electric field detection.

[0087] It is understandable that since this electronic device includes the chopper amplifier circuit in the above embodiments, it has all the beneficial effects brought about by the above chopper amplifier circuit technical solution, which will not be repeated here.

[0088] The above description is merely an optional embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A chopper amplifier circuit, characterized in that, include: The transformer switching amplifier module (100) is used to modulate the input signal and amplify the modulated signal in the first stage. The differential amplifier and filter module (200) is used to amplify the signal output by the transformer switch amplifier module (100) in the second stage and perform high-pass filtering on the amplified signal in the second stage. The demodulation module (300) is used to demodulate the signal output by the differential amplification and filtering module (200) and feed the demodulated signal back to the transformer switching amplification module (100).

2. The chopper amplifier circuit according to claim 1, characterized in that, The transformer switching amplifier module (100) includes: First capacitor (C1); The first transformer (T1) and the second transformer (T2) are used to receive the input signal. The in-phase terminal of the primary side of the first transformer (T1) and the out-of-phase terminal of the primary side of the second transformer (T2) are grounded through the first capacitor (C1). The in-phase terminal of the secondary side of the first transformer (T1) and the in-phase terminal of the secondary side of the second transformer (T2) are connected to the differential amplifier and filter module (200) to output the modulated and first-stage amplified signal. A first switch (Q1) and a second switch (Q2) are connected. The first end of the first switch (Q1) is connected to the inverting terminal of the primary side of the first transformer (T1), and the first end of the second switch (Q2) is connected to the non-inverting terminal of the primary side of the second transformer (T2). The second end of the first switch (Q1) and the second end of the second switch (Q2) are connected to the demodulation module (300). The control terminals of the first switch (Q1) and the second switch (Q2) are used to receive a first control signal and a second control signal, respectively. The first control signal and the second control signal are in an inverted state.

3. The chopper amplifier circuit according to claim 2, characterized in that, The transformer switching amplifier module (100) also includes: The first resistor (R1) has one end connected to the control terminal of the first switching transistor (Q1), and the other end of the first resistor (R1) is grounded. The second resistor (R2) has one end connected to the control terminal of the second switch (Q2), and the other end grounded.

4. The chopper amplifier circuit according to claim 2, characterized in that, The frequencies of the first control signal and the second control signal are greater than or equal to And the larger of 100Hz, among which, This indicates the frequency of the input signal.

5. The chopper amplifier circuit according to claim 2, characterized in that, The differential amplification and filtering module (200) includes: The first differential amplifier unit (210) has its first input terminal connected to the in-phase terminal of the secondary side of the first transformer (T1), its second input terminal connected to the in-phase terminal of the secondary side of the second transformer (T2), and its first and second output terminals used to output the signal amplified by the second stage. The first filter unit (220) has its first input terminal connected to the first output terminal of the first differential amplifier unit (210), its second input terminal connected to the second output terminal of the first differential amplifier unit (210), and its first and second output terminals connected to the demodulation module (300) for outputting the high-pass filtered signal.

6. The chopper amplifier circuit according to claim 5, characterized in that, The differential amplification and filtering module (200) further includes: A buffer unit (230) is connected between the first differential amplifier unit (210) and the first filter unit (220).

7. The chopper amplifier circuit according to claim 5, characterized in that, The first differential amplifier unit (210) includes: The third switch (Q3) and the fourth switch (Q4) are connected, with the control terminal of the third switch (Q3) connected to the in-phase terminal of the secondary side of the first transformer (T1) and the control terminal of the fourth switch (Q4) connected to the in-phase terminal of the secondary side of the second transformer (T2). The first terminal of the third switch (Q3) is connected to the first input terminal of the first filter unit (220), and the first terminal of the fourth switch (Q4) is connected to the second input terminal of the first filter unit (220). The third resistor (R3) is connected between the first terminal of the third switch (Q3) and the power supply. The fourth resistor (R4) is connected between the first terminal of the fourth switch (Q4) and the power supply. A constant current source (I1) is provided, and the second terminals of the third switch (Q3) and the fourth switch (Q4) are grounded through the constant current source (I1).

8. The chopper amplifier circuit according to claim 5, characterized in that, The cutoff frequency range of the first filter unit (220) is [100Hz, f SW ], where f SW This indicates the frequency of the first control signal.

9. The chopper amplifier circuit according to claim 2, characterized in that, The transformer switching amplifier module (100) also includes: The first feedback resistor (R5) has one end connected to the second end of the first switch (Q1) and the second end of the second switch (Q2), and the other end of the first feedback resistor (R5) is grounded. The demodulation module (300) includes: A full-bridge switching unit (310) includes a first analog switch (S1), a second analog switch (S2), a third analog switch (S3), and a fourth analog switch (S4). The first terminal of the first analog switch (S1) and the first terminal of the third analog switch (S3) are connected to form a first connection node. The first terminal of the second analog switch (S2) and the first terminal of the fourth analog switch (S4) are connected to form a second connection node. The first connection node and the second connection node are connected to the differential amplifier and filter module (200) to receive the signal output by the differential amplifier and filter module (200). The second differential amplifier unit (320) has its first input terminal connected to the second terminal of the third analog switch (S3) and the second terminal of the fourth analog switch (S4), respectively. The second input terminal of the second differential amplifier unit (320) is connected to the second terminal of the first analog switch (S1) and the second terminal of the second analog switch (S2), respectively. The output terminal of the second differential amplifier unit (320) is used to output the demodulated signal. An output feedback unit (330) is provided, the input terminal of which is connected to the output terminal of the second differential amplifier unit (320). The first output terminal of the output feedback unit (330) is connected to the second terminal of the first switch (Q1) and the second terminal of the second switch (Q2) respectively, for feeding back the demodulated signal to the transformer switch amplifier module (100). The second output terminal of the output feedback unit (330) is used to output the demodulated signal. The first analog switch (S1) and the fourth analog switch (S4) are controlled by a third control signal, and the second analog switch (S2) and the third analog switch (S3) are controlled by a fourth control signal. The duration of the high level of the first control signal covers the duration of the high level of the third control signal, and the duration of the high level of the second control signal covers the duration of the high level of the fourth control signal.

10. The chopper amplifier circuit according to claim 9, characterized in that, The high-level start time of the third control signal is delayed by t1 time compared to the high-level start time of the first control signal, and the high-level end time of the third control signal is advanced by t2 time compared to the high-level end time of the first control signal. The high-level start time of the fourth control signal is delayed by t3 hours compared to the high-level start time of the second control signal, and the high-level end time of the fourth control signal is advanced by t4 hours compared to the high-level end time of the second control signal. Wherein, the durations t1 and t3 are both greater than the turn-on durations of the first switch (Q1) and the second switch (Q2), and the durations t2 and t4 are both greater than the turn-off durations of the first switch (Q1) and the second switch (Q2).

11. The chopper amplifier circuit according to claim 9, characterized in that, The output feedback unit (330) includes: An output resistor (R6) is provided, one end of which is connected to the output terminal of the second differential amplifier unit (320). The second feedback resistor (R7) has one end connected to the other end of the output resistor (R6), and the other end of the second feedback resistor (R7) is connected to the second end of the first switch (Q1) and the second end of the second switch (Q2). The second capacitor (C2) is connected in parallel across the second feedback resistor (R7).

12. The chopper amplifier circuit according to claim 9, characterized in that, The demodulation module (300) further includes: The second filtering unit (340) is connected between the output terminal of the second differential amplifier unit (320) and the input terminal of the output feedback unit (330); Wherein, the cutoff frequency of the second filter unit (340) is greater than or equal to ,in, This indicates the frequency of the input signal.

13. An electronic device, characterized in that, include: The chopper amplifier circuit as described in any one of claims 1 to 12.

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