CN218041376U - Two-stage amplifying circuit - Google Patents

Abstract

The application relates to a secondary amplification circuit, which comprises a signal input end, a primary filtering unit for filtering high-frequency signals, a primary amplification adjusting unit for performing primary amplification on the signals after primary filtering, a secondary amplification adjusting unit for performing secondary amplification on the signals after primary amplification, a reference voltage unit for providing reference voltage for the primary amplification adjusting unit and the secondary amplification adjusting unit, and a final filtering unit for performing secondary filtering on the signals after secondary amplification. The method and the device have the effect of reducing the higher frequency signal attenuation to cause the acquisition to have larger errors.

Description

Two-stage amplification circuit

Technical Field

The application relates to the field of sensor application circuits, in particular to a secondary amplifying circuit.

Background

Microwave doppler technology is commonly used in detecting moving objects, and a microwave receiver acquires microwave signals reflected by the objects and analyzes doppler signals output by the microwave receiver to determine whether the objects move and the moving speed. The doppler signal output by the microwave receiver is very weak, and the processor cannot directly process the signal, and needs to perform further amplification processing and remove the interference of the high-frequency signal.

Currently, a low-pass filtering and amplifying circuit is generally arranged between the microwave receiver and the processor to amplify and filter the doppler signal. The existing low-pass filtering and amplifying circuit filters useless high-frequency signals, and meanwhile, because high-frequency noise is more, useful higher-frequency signals in filtered Doppler signals also generate more serious signal attenuation, and the output voltage value of the existing low-pass filtering and amplifying circuit is lower, so that the existing low-pass filtering and amplifying circuit cannot be directly input into a controller for analysis. Therefore, the acquisition of the processor to the higher frequency signal frequency is far lower than the actual acquisition, and errors occur in partial data acquisition of the control chip.

SUMMERY OF THE UTILITY MODEL

In order to reduce the large error of data acquisition caused by the attenuation of a high-frequency signal, the application provides a two-stage amplifying circuit.

The application provides a two-stage amplification circuit, adopts following technical scheme:

a secondary amplification circuit comprises a primary filtering unit, a secondary amplification unit and a primary amplification unit, wherein the primary filtering unit comprises a primary filtering input end and a primary filtering output end, the primary filtering input end is used for receiving an external signal, and the primary filtering output end outputs a primary filtering signal;

a reference voltage unit including a reference voltage terminal for providing a reference voltage;

the first-stage amplification regulating unit comprises a first input end, a second input end and a first output end, wherein the first input end is connected to the primary filtering output end to receive a primary filtering signal, the second input end is connected to the reference voltage end to obtain reference voltage, and the first output end outputs a first-stage amplification signal;

the second-stage amplification regulating unit comprises a third input end, a fourth input end and a second output end, wherein the third input end is coupled to the first output end to receive the first-stage amplification signal, the fourth input end is connected to the reference voltage end to obtain reference voltage, and the second output end outputs a second-stage amplification signal;

and the final-order filtering unit comprises a final-order filtering input end and a final-order filtering output end, the final-order filtering input end is connected to the first output end to receive the two-stage amplified signal, and the final-order filtering output end outputs a final-order filtering signal.

By adopting the technical scheme, the Doppler signal enters from the primary filtering input end, is subjected to low-pass filtering by the primary filtering unit, is filtered to remove high-frequency noise, and enters the primary amplification regulating unit to carry out primary voltage amplification after effective frequency is reserved; the second-stage amplification regulating unit is used for carrying out voltage amplification on the signals processed by the first-stage amplification regulating unit so as to improve a voltage output value, and meanwhile, the second-stage amplification unit is used for regulating the signals processed by the first-stage amplification regulating unit so as to maintain the stability of the signals at higher frequency; and finally, the amplified and adjusted signals are filtered again by the final-stage filtering unit, so that the stability of the output signals is further improved.

Optionally, the primary filtering unit includes a primary filtering resistor R1, a primary filtering capacitor C1, a secondary filtering capacitor C2, and a dc blocking capacitor C3; the primary filter resistor R1 is connected with the blocking capacitor C3 in series, the other end of the primary filter resistor C1 is a primary filter input end for receiving external signals, and the other end of the blocking capacitor C3 is a primary filter output end for outputting primary filter signals; one end of the first-stage filter capacitor C1 is connected to a connection node between the first-stage filter resistor R1 and the blocking capacitor C3, the other end of the first-stage filter capacitor C1 is connected to a power ground, one end of the second-stage filter capacitor C2 is connected to the primary-stage filter output end, and the other end of the second-stage filter capacitor C2 is connected to the power ground.

By adopting the technical scheme, the input Doppler signal is subjected to primary low-pass filtering so as to reduce high-frequency noise signals in the signal.

Optionally, the reference voltage unit includes a first bias resistor R2, a second bias resistor R3, and a first decoupling capacitor C4, the first bias resistor R2 and the second bias resistor R3 are sequentially connected in series between a positive electrode of a power supply and a power ground, the first decoupling capacitor C4 is connected in parallel with the second bias resistor R3, and a connection node between the first bias resistor R2 and the second bias resistor R3 is a reference voltage end.

Through adopting above-mentioned technical scheme, reference voltage sudden change can be prevented to first decoupling capacitor.

Optionally, the first-stage amplification and adjustment unit includes a first operational amplifier U1, a first reference resistor R4, a feedback resistor R5, and a vibration-damping capacitor C5; the first operational amplifier U1 comprises a first non-inverting input end, a first inverting input end and a first amplifying output end, and the vibration-eliminating capacitor C5 is connected between the first inverting input end and the first amplifying output end; one end of the first reference resistor R4 is connected to the first inverting input end, and the other end of the first reference resistor R4 is a first input end and receives a primary-order filtering signal; one end of the feedback resistor R5 is connected to the first amplification output end, and the other end of the feedback resistor R5 is connected to the first input end; the first amplification output end outputs a first-stage amplification signal, and the first in-phase input end is connected to the reference voltage end to obtain reference voltage.

By adopting the technical scheme, the first reference resistor R5 provides a reference voltage for the primary-order filtering signal, so that the first operational amplifier U1 can conveniently carry out amplification operation.

Optionally, the second-stage amplification and adjustment unit includes a second operational amplifier U2, a second reference resistor R6, an integral feedback resistor R7, and an integral feedback capacitor C6; the second operational amplifier U2 comprises a second non-inverting input end, a second inverting input end and a second amplifying output end, one end of the second reference resistor R6 is connected to the first output end to receive a first-stage amplifying signal, and the other end of the second reference resistor R6 is connected to the second inverting input end; the integral feedback resistor R7 is connected between the second amplification output end and the second inverting input end, and the integral feedback resistor R7 is connected with the integral feedback capacitor C6 in parallel; the second non-inverting input end is connected to the reference voltage input end to obtain reference voltage, and the second amplification output end outputs a two-stage amplification signal.

By adopting the technical scheme, the integral feedback resistor R7 and the integral feedback capacitor C6 form an RC integral regulating circuit so as to reduce the attenuation of the output signal of the output end.

Optionally, the final-order filtering unit includes a final-order filtering resistor R8 and a final-order filtering capacitor C7, one end of the final-order filtering resistor R8 is connected to the second output end to receive the second-stage amplified signal, the other end of the final-order filtering resistor R8 outputs the final-order filtered signal, and the final-order filtering capacitor C7 is connected between the other end of the final-order filtering resistor R8 and a power ground.

Optionally, the two-stage amplification circuit further comprises a notch unit connected between the first output terminal and the third input terminal.

By adopting the technical scheme, the trap wave unit is connected between the first-stage amplification regulating unit and the second-stage amplification regulating unit, and before the signal is subjected to secondary amplification, the interference signal with specific frequency is filtered.

Optionally, the trap unit includes a low-pass capacitor C11, a first low-pass resistor R11, a second low-pass resistor R12, a high-pass resistor R13, a first high-pass capacitor C9, and a second high-pass capacitor C10; the first low-pass resistor R11 and the second low-pass resistor R12 are connected in series, one end of the low-pass capacitor C11 is connected to a connection node between the first low-pass resistor R11 and the second low-pass resistor R12, and the other end of the low-pass capacitor C11 is connected to a power ground; the first high-pass capacitor C9 is connected with the second high-pass capacitor C10 in series, one end of the high-pass resistor R13 is connected to a connection node between the first high-pass capacitor C9 and the second high-pass capacitor C10, and the other end of the high-pass resistor R13 is connected to a power ground; the first low-pass resistor R11 is connected to the first high-pass capacitor C9, and the connection node is connected to the first output terminal, and the second low-pass resistor R12 is connected to the second high-pass capacitor C10, and the connection node is connected to the third input terminal.

By adopting the technical scheme, the low-pass capacitor, the first low-pass resistor and the second low-pass resistor form a low-pass filter circuit, the high-pass resistor, the first high-pass capacitor and the second high-pass capacitor form a high-pass filter circuit, and the low-pass filter circuit and the high-pass filter circuit are connected in parallel to form a T-shaped notch filter circuit so as to filter signals of 50HZ or 100HZ in the signals and reduce signal interference.

In summary, the present application includes at least one of the following beneficial technical effects:

1. the output voltage in the Doppler signal can be effectively improved, and the Doppler signal is convenient to process by a processor;

2. can filter 50HZ or 100 HZ's in the signal power frequency signal interference, promote signal processing stability.

Drawings

Fig. 1 is a schematic diagram of a two-stage amplifier circuit according to embodiment 1 of the present application.

Fig. 2 is a schematic diagram of a two-stage amplifying circuit according to embodiment 2 of the present application.

Fig. 3 is a schematic diagram of a two-stage amplifying circuit according to embodiment 3 of the present application.

Fig. 4 is a schematic diagram of a two-stage amplifying circuit according to embodiment 4 of the present application.

Description of reference numerals: 1. a primary filtering unit; 2. a reference voltage unit; 3. a first-stage amplification regulating unit; 4. a secondary amplification regulating unit; 5. a last order filtering unit; 6. a trap unit.

Detailed Description

The present application is described in further detail below with reference to figures 1-4.

At present, a moving human body is generally detected by microwave induction, a microwave receiver receives microwave signals reflected by the human body and outputs Doppler signals to a processor for data processing, and different frequencies in the acquired Doppler signals generally correspond to different walking speeds of the human body. The existing method can be roughly divided into slow walking at 7-18Hz, normal walking at 18-28Hz and quick walking at 28-45 Hz.

However, the doppler signal output by the microwave receiver has a small output voltage and high frequency signal interference, so the embodiment of the present application discloses a two-stage amplifying circuit, which is configured to amplify the doppler signal and filter the high frequency interference while arranging a two-stage amplifying circuit with low pass filtering between the doppler signal output by the microwave receiver and the processor.

Example 1

Referring to fig. 1, a secondary amplification circuit includes a primary filtering unit 1, a reference voltage unit 2, a primary amplification adjusting unit 3, a secondary amplification adjusting unit 4, and a final filtering unit 5. After receiving the doppler signal, the primary filtering unit 1 filters a high-frequency signal higher than the human body walking frequency in the doppler signal and outputs a primary filtering signal; the first-stage amplification regulating unit 3 compares and amplifies the received primary-stage filtering signal and a reference voltage signal obtained from the reference voltage unit 2, and outputs a first-stage amplification signal; the Doppler signals after primary amplification enter a secondary amplification regulating unit 4 for secondary amplification, and output signals are regulated through the secondary amplification regulating unit 4, so that the stability of the signals output by the secondary amplification regulating unit 4 is improved; then, the Doppler signals are input into a final-order filtering unit, filtering processing is carried out on the Doppler signals amplified twice, and final-order filtering signals are output. The frequency of the Doppler signal is gradually stabilized by the adjusting action of the two-stage amplification adjusting unit 4, so that the error of data acquisition at higher frequency is reduced, and the voltage output value of the Doppler signal is improved.

The primary filtering unit 1 comprises a primary filtering resistor R1, a primary filtering capacitor C1, a secondary filtering capacitor C2 and a blocking capacitor C3. The primary filter resistor R1 is connected with the blocking capacitor C3 in series, and the other end of the primary filter resistor R1 is a primary filter input end for receiving an external signal; the other end of the blocking capacitor C3 is a primary filtering output end to output a primary filtering signal. The primary filter capacitor C1 is connected between the connection node of the primary filter resistor R1 and the DC blocking capacitor C3 and the power ground; two ends of the second-stage filter capacitor C2 are connected between the first-stage filter output end and the power ground. The primary filter resistor R1 and the primary filter capacitor C1 form a primary RC filter circuit, and primary low-pass filtering is performed on the input Doppler signal to filter a higher-frequency signal in the input signal; the direct current signal in the Doppler signal can be filtered by the direct current blocking capacitor C3; the second-stage filter capacitor C2 re-filters the multiple input signals to filter out lower-frequency signals in the input signals, so as to output a first-order filtered signal with a specific frequency.

The reference voltage unit 2 includes a first bias resistor R2, a second bias resistor R3, and a first decoupling capacitor C4. The first bias resistor R2 and the second bias resistor R3 are connected in series, the other end of the first bias resistor R2 is connected with the positive electrode of a power supply, the other end of the second bias resistor R3 is connected with the ground of the power supply, and the first decoupling capacitor C4 is connected with the second bias resistor R3 in parallel. In this embodiment, the voltage of the positive electrode of the power supply is +5V, and the connection node between the first bias resistor R2 and the second bias resistor R3 is the reference voltage terminal. The first decoupling capacitor C4 can prevent the reference voltage from abruptly changing.

The first-stage amplification adjusting unit 3 comprises a first operational amplifier U1, a first reference resistor R4, a feedback resistor R5 and a vibration-eliminating capacitor C5. The first operational amplifier U1 comprises a first inverting input end, a first non-inverting input end and a first amplifying output end, and the vibration-eliminating capacitor C5 is connected between the first amplifying output end and the first inverting input end. One end of the first reference resistor R4 is connected to the first inverting input terminal, and the other end of the first reference resistor R4 is a first input terminal and connected to the first-order filtering output terminal to receive the first-order filtering signal. One end of the feedback resistor R5 is connected with the first amplifying output end, and the other end of the feedback resistor R5 is connected with the first input end. The first non-inverting input terminal is a second input terminal of the first-stage amplifying and adjusting unit 3 and is connected to the reference voltage terminal to obtain the reference voltage. The first amplification output end is a first output end of the first-stage amplification adjusting unit 3. The primary filtering signal enters the first inverting input end through the first reference resistor R4, is compared and amplified with the reference voltage of the first non-inverting input end, and finally, a primary amplification signal is output through the first amplification output end.

The secondary amplification regulating unit 4 comprises a second operational amplifier U2, a second reference resistor R6, an integral feedback resistor R7 and an integral feedback capacitor C6. The second operational amplifier U2 comprises a second inverting input end, a second non-inverting input end and a second amplifying output end, the integral feedback resistor R7 is connected between the second amplifying output end and the second inverting input end, and the second integral feedback capacitor C6 is connected with the second integral feedback resistor R7 in parallel. One end of the second reference resistor R6 is connected to the second inverting input terminal, and the other end of the second reference resistor R6 is a third input terminal and connected to the first output terminal to receive the one-stage amplified signal. The second non-inverting input terminal is a fourth input terminal of the two-stage amplification regulating unit 4 and is connected to the reference voltage terminal to obtain the reference voltage, and the second amplification output terminal is a second output terminal of the two-stage amplification regulating unit 4. The first-stage amplification signal is input through the second inverting input end, then is compared with the reference voltage for amplification, and the second-stage amplification signal is output through the second amplification output end. The integral feedback resistor R7 and the integral feedback capacitor C6 form an RC integral feedback regulating circuit, and mainly perform feedback filtering on a secondary amplification signal at the second amplification output end to prevent the output signal at the second amplification output end from generating sudden change.

The last-order filtering unit 5 comprises a last-order filtering resistor R8 and a last-order filtering capacitor C7, wherein one end of the last-order filtering resistor R8 is a last-order filtering input end and is connected to the second output end, and the other end of the last-order filtering resistor R8 is a last-order filtering output end and is used for being connected with a controller to output a last-order filtering signal. A final filter capacitor C7 is connected between the final filter output and power ground. And the final-order filter resistor R8 and the final-order filter capacitor C7 filter the secondarily amplified signals, so that the interference of the signals is further reduced.

The implementation principle of the embodiment 1 of the application is as follows: the Doppler signals enter from the primary filtering input end, are subjected to low-pass filtering by the primary filtering unit 1, are filtered to remove frequencies higher than the walking frequency of a human body, retain effective frequencies, then enter the primary amplification adjusting unit 3 for amplification, then enter the secondary amplification adjusting unit 4 for secondary amplification, and the final filtering unit 5 is used for low-pass filtering on the amplified signals. And aiming at the attenuation of higher frequency signals, the secondary amplification regulating unit 4 prevents the voltage value from suddenly changing and feeding back through the integral regulation of an RC integral feedback circuit. And the final output signal voltage value is ensured to be close to the original value through two times of amplification. However, the microwave sensor feeds back the movement of an object by detecting the frequency value of the waveform signal and ensures that the signal attenuation is small when the microwave sensor is finally output by RC feedback adjustment in the secondary amplification adjusting unit 4, thereby solving the problems of acquisition error and low output voltage value caused by high-frequency signal attenuation in the existing second-order low-pass filtering amplifying circuit.

Example 2

Referring to fig. 2, the difference between this embodiment and embodiment 1 is that the primary filter unit 1 further includes a secondary filter resistor R9, and the reference voltage unit 2 further includes a second decoupling capacitor C8. The secondary filter resistor R9 is connected in series between the primary filter output end and the secondary filter capacitor C2 and is used for inhibiting the influence caused by current transient in the secondary filter capacitor C2. The second decoupling capacitor C8 is connected between the positive power supply and the power ground for absorbing noise in the power supply and reducing interference to the circuit.

Example 3

Referring to fig. 3, this embodiment is different from embodiment 1 in that the two-stage method circuit further includes a notch unit 6, and the notch unit 6 is connected between the first output terminal and the third input terminal. The trap unit 6 includes a low-pass capacitor C11, a first low-pass resistor R11, a second low-pass resistor R12, a high-pass resistor R13, a first high-pass capacitor C9, and a second high-pass capacitor C10. The first low-pass resistor R11 and the second low-pass resistor R12 are connected in series, one end of the low-pass capacitor C11 is connected to a connection node between the first low-pass resistor R11 and the second low-pass resistor R12, and the other end of the low-pass capacitor C11 is connected to the power ground. The first high-pass capacitor C9 is connected with the second high-pass capacitor C10 in series, one end of the high-pass resistor R13 is connected to a connection node between the first high-pass capacitor C9 and the second high-pass capacitor C10, and the other end of the high-pass resistor R13 is connected to the power ground. The first low-pass resistor R11 is connected with the first high-pass capacitor C9, the connecting node is connected with the first output end, the second low-pass resistor R12 is connected with the second high-pass capacitor C10, and the connecting node is connected with the third input end. The low-pass capacitor C11, the first low-pass resistor R11 and the second low-pass resistor R12 jointly form a low-pass filter circuit, the high-pass resistor R13, the first high-pass capacitor C9 and the second high-pass capacitor C10 jointly form a high-pass filter circuit, and the low-pass filter circuit and the high-pass filter circuit are connected in parallel to form a notch filter circuit so as to filter signals of 50HZ or 100HZ in the signals.

The implementation principle of embodiment 3 of the application is as follows: doppler signals enter from a primary filtering input end, after effective frequency is reserved through low-pass filtering of a primary filtering unit 1, the Doppler signals enter a primary amplification regulating unit 3 for amplification, then enter a notch unit 6 for filtering power frequency interference of 50HZ or 100HZ, then enter a secondary amplification regulating unit 4 for secondary amplification, and finally, the amplified signals are subjected to low-pass filtering through a final filtering unit 5. And aiming at the attenuation of higher frequency signals, the secondary amplification regulating unit 4 prevents the voltage value from sudden change and feeding back through integral regulation of an RC integral feedback circuit. And the final output signal voltage value is close to the original value through two times of amplification. However, the microwave sensor feeds back the movement of an object by detecting the frequency value of the waveform signal and ensures that the signal attenuation is small when the microwave sensor is finally output by RC feedback adjustment in the secondary amplification adjusting unit 4, thereby solving the problems of acquisition error and low output voltage value caused by high-frequency signal attenuation in the existing second-order low-pass filtering amplifying circuit.

Example 4

Referring to fig. 4, the difference between this embodiment and embodiment 3 is that the primary filter unit 1 further includes a secondary filter resistor R9, and the reference voltage unit 2 further includes a second decoupling capacitor C8. The secondary filter resistor R9 is connected in series between the primary filter output end and the secondary filter capacitor C2 and is used for inhibiting the influence caused by current transient in the secondary filter capacitor C2. The second decoupling capacitor C8 is connected between the positive power supply and the power ground for absorbing noise in the power supply and reducing interference to the circuit.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (8)

1. A two-stage amplification circuit, comprising:

the primary filtering unit (1) comprises a primary filtering input end and a primary filtering output end, wherein the primary filtering input end is used for receiving an external signal, and the primary filtering output end outputs a primary filtering signal;

a reference voltage unit (2) including a reference voltage terminal for providing a reference voltage;

the first-stage amplification regulating unit (3) comprises a first input end, a second input end and a first output end, wherein the first input end is connected to the primary filtering output end to receive a primary filtering signal, the second input end is connected to the reference voltage end to obtain reference voltage, and the first output end outputs a first-stage amplification signal;

the second-stage amplification regulating unit (4) comprises a third input end, a fourth input end and a second output end, wherein the third input end is coupled to the first output end to receive the first-stage amplification signal, the fourth input end is connected to the reference voltage end to obtain reference voltage, and the second output end outputs a second-stage amplification signal;

and the final-order filtering unit (5) comprises a final-order filtering input end and a final-order filtering output end, the final-order filtering input end is connected to the second output end to receive the second-stage amplified signal, and the final-order filtering output end outputs a final-order filtering signal.

2. The two-stage amplification circuit of claim 1, wherein: the primary filtering unit (1) comprises a primary filtering resistor R1, a primary filtering capacitor C1, a secondary filtering capacitor C2 and a blocking capacitor C3; the primary filter resistor R1 is connected in series with the blocking capacitor C3, the other end of the primary filter resistor R1 is a primary filter input end for receiving an external signal, and the other end of the blocking capacitor C3 is a primary filter output end for outputting a primary filter signal; one end of the first-stage filter capacitor C1 is connected to a connection node between the first-stage filter resistor R1 and the DC blocking capacitor C3, the other end of the first-stage filter capacitor C1 is connected to a power ground, one end of the second-stage filter capacitor C2 is connected to the primary filter output end, and the other end of the second-stage filter capacitor C2 is connected to the power ground.

3. The two-stage amplification circuit of claim 1, wherein: the reference voltage unit (2) comprises a first biasing resistor R2, a second biasing resistor R3 and a first decoupling capacitor C4, the first biasing resistor R2 and the second biasing resistor R3 are sequentially connected in series between a power supply anode and a power supply ground, the first decoupling capacitor C4 is connected with the second biasing resistor R3 in parallel, and a connection node between the first biasing resistor R2 and the second biasing resistor R3 is a reference voltage end.

4. The two-stage amplification circuit of claim 1, wherein: the primary amplification adjusting unit (3) comprises a first operational amplifier U1, a first reference resistor R4, a feedback resistor R5 and a vibration eliminating capacitor C5; the first operational amplifier U1 comprises a first non-inverting input end, a first inverting input end and a first amplifying output end, and the vibration-eliminating capacitor C5 is connected between the first inverting input end and the first amplifying output end; one end of the first reference resistor R4 is connected to the first inverting input end, and the other end of the first reference resistor R4 is a first input end and receives a primary-order filtering signal; one end of the feedback resistor R5 is connected to the first amplification output end, and the other end of the feedback resistor R5 is connected to the first input end; the first amplification output end outputs a first-stage amplification signal, and the first in-phase input end is connected to the reference voltage end to obtain reference voltage.

5. The two-stage amplification circuit of claim 1, wherein: the secondary amplification regulating unit (4) comprises a second operational amplifier U2, a second reference resistor R6, an integral feedback resistor R7 and an integral feedback capacitor C6; the second operational amplifier U2 comprises a second non-inverting input end, a second inverting input end and a second amplifying output end, one end of the second reference resistor R6 is connected to the first output end to receive a first-stage amplifying signal, and the other end of the second reference resistor R6 is connected to the second inverting input end; the integral feedback resistor R7 is connected between the second amplification output end and the second inverting input end, and the integral feedback resistor R7 is connected with the integral feedback capacitor C6 in parallel; the second non-inverting input end is connected to the reference voltage input end to obtain a reference voltage, and the second amplification output end outputs a two-stage amplification signal.

6. The two-stage amplification circuit of claim 1, wherein: the final-order filtering unit (5) comprises a final-order filtering resistor R8 and a final-order filtering capacitor C7, one end of the final-order filtering resistor R8 is connected to the second output end to receive the second-stage amplified signal, the other end of the final-order filtering resistor R8 outputs a final-order filtering signal, and the final-order filtering capacitor C7 is connected between the other end of the final-order filtering resistor R8 and a power ground.

7. The two-stage amplification circuit of claim 1, wherein: further comprising a notch unit (6), said notch unit (6) being connected between said first output terminal and said third input terminal.

8. The two-stage amplification circuit of claim 7, wherein: the trap unit (6) comprises a low-pass capacitor C11, a first low-pass resistor R11, a second low-pass resistor R12, a high-pass resistor R13, a first high-pass capacitor C9 and a second high-pass capacitor C10; the first low-pass resistor R11 and the second low-pass resistor R12 are connected in series, one end of the low-pass capacitor C11 is connected to a connection node between the first low-pass resistor R11 and the second low-pass resistor R12, and the other end of the low-pass capacitor C11 is connected to a power ground; the first high-pass capacitor C9 is connected with the second high-pass capacitor C10 in series, one end of the high-pass resistor R13 is connected to a connection node between the first high-pass capacitor C9 and the second high-pass capacitor C10, and the other end of the high-pass resistor R13 is connected to a power ground; the first low-pass resistor R11 is connected to the first high-pass capacitor C9, and the connection node is connected to the first output terminal, and the second low-pass resistor R12 is connected to the second high-pass capacitor C10, and the connection node is connected to the third input terminal.

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