CN106849903B

CN106849903B - Frequency filter circuit

Info

Publication number: CN106849903B
Application number: CN201611230553.1A
Authority: CN
Inventors: 乐东岳; 张国锐
Original assignee: Ningbo Sikaile Intelligent Technology Co ltd
Current assignee: Ningbo Sikaile Intelligent Technology Co ltd
Priority date: 2016-12-28
Filing date: 2016-12-28
Publication date: 2020-12-22
Anticipated expiration: 2036-12-28
Also published as: CN106849903A

Abstract

The invention discloses a frequency filter circuit, which obtains good sensitivity through the cooperation of multistage operational amplifiers, filters mixed power supply frequency noise when amplifying weak signals, ensures the effectiveness and anti-interference performance of filtering, improves a Q value through the operational amplifiers and positive feedback to reduce the filtering loss of the circuit, and prevents electromagnetic interference; the frequency can be adjusted by a potentiometer to reduce the output voltage, thereby preventing the reduction of the resonant frequency caused by the dispersion of the capacitor.

Description

Frequency filter circuit

Technical Field

The invention relates to the field of filtering, in particular to a frequency filtering circuit.

Background

The frequency spectrum of conducted noise of one of the power frequency noise and the ten electromagnetic interference is approximately 10 kHz-30 MHz, and the highest frequency spectrum can even reach 150 MHz; the power frequency noise, especially the transient noise interference, has fast rising speed, short duration, high voltage amplitude and strong randomness, and is very easy to generate serious interference to the circuit.

Disclosure of Invention

The invention provides a frequency filter circuit for filtering noise of a power supply frequency.

The invention is realized by the following technical scheme: a frequency filter circuit comprises an input port, an output port, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a fourteenth capacitor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, an eighteenth capacitor, a nineteenth capacitor, a twentieth capacitor, a twenty-first capacitor, a first potentiometer, a second resistor, a fifth resistor, a sixth resistor, a seventh resistor, a seventeenth resistor, a nineteenth resistor, a twentieth resistor, The second potentiometer, the first triode, the second triode, the first operational amplifier, the second operational amplifier, the third operational amplifier, the fourth operational amplifier, the fifth operational amplifier, the sixth operational amplifier and the VCC power supply; the input port is connected with one end of a first resistor, the other end of the first resistor is further connected to a collector of a first triode, a second resistor is connected in series between a base electrode and an emitter of the first triode, the collector of the first triode is further connected to a base electrode of a second triode, the base electrode of the first triode is further connected to an emitter of the second triode, the collector of the second triode is connected with one end of a first capacitor, one end of the first capacitor is further connected to one end of a second capacitor, one end of the second capacitor is further connected to one end of a third resistor, the other ends of the first capacitor, the second capacitor and the third resistor are all grounded, one end of the third resistor is further connected to a positive input end of the first operational amplifier, a negative input end of the first operational amplifier is connected with one end of a fourth resistor, and the other end of the fourth resistor is connected to an output end of the first operational amplifier, the fourth resistor is also connected with a third capacitor in parallel, the output end of the first operational amplifier is connected to one end of a first potentiometer, the other end of the first potentiometer is connected with an eighth resistor, the other end of the eighth resistor is grounded, the output end of the first operational amplifier is also connected to one end of a fifth resistor, the other end of the fifth resistor is connected with one end of a sixth resistor, the other end of the sixth resistor is connected with the positive input end of the second operational amplifier, the other end of the sixth resistor is also connected to one end of an eighth capacitor, the other end of the eighth capacitor is connected to one end of a sixth capacitor, the other end of the sixth capacitor is connected with the variable resistance end of the first potentiometer, the other end of the eighth capacitor is also connected to one end of a seventh resistor, the other end of the seventh resistor is connected to one end of a seventh capacitor, and the other end of the seventh capacitor is connected to one end of the sixth resistor, the negative input end of the second operational amplifier is connected with the output end of the second operational amplifier, the output end of the second operational amplifier is connected with one end of a ninth resistor, the other end of the seventh resistor is further connected with the output end of a third operational amplifier, the output end of the third operational amplifier is further connected with the negative input end of a third operational amplifier, the positive input end of the third operational amplifier is connected with one end of a tenth resistor, the other end of the tenth resistor is grounded, one end of the tenth resistor is further connected with one end of an eleventh resistor, the other end of the eleventh resistor is connected with one end of an eleventh capacitor, the other end of the ninth resistor is also connected with one end of an eleventh capacitor, the other end of the eleventh capacitor is grounded, one end of the eleventh capacitor is further connected with one end of a thirteenth resistor, one end of the thirteenth resistor is further connected with one end of a second potentiometer, and the other end of the second potentiometer is connected with one end of a fourteenth resistor, the other end of the thirteenth resistor is connected with one end of a twelfth resistor, the other end of the twelfth resistor is connected with one end of a fourteenth capacitor, the other end of the fourteenth capacitor is connected with one end of the twelfth capacitor, the other end of the twelfth capacitor is connected with a resistance-changing end of a second potentiometer, the other end of the thirteenth resistor is also connected with one end of a thirteenth capacitor, the other end of the thirteenth capacitor is connected with one end of a fifteenth resistor, the other end of the fifteenth resistor is connected with the other end of the fourteenth capacitor, one end of the fifteenth resistor is also connected with an output end of a fifth operational amplifier, an output end of the fifth operational amplifier is connected with a negative input end of the fifth operational amplifier, a positive input end of the fifth operational amplifier is connected with one end of a seventeenth resistor, the other ends of the seventeenth resistor and the fourteenth resistor are both grounded, and one end of the seventeenth resistor is also connected with one end of an eighteenth resistor, the other end of the eighteenth resistor is connected with one end of a seventeenth capacitor, the other end of the seventeenth capacitor is grounded, one end of the seventeenth capacitor is also connected with one end of a sixteenth resistor, the other end of the sixteenth resistor is connected with the output end of a fourth operational amplifier, the output end of the fourth operational amplifier is connected with the negative input end of the fourth operational amplifier, and the positive input end of the fourth operational amplifier is connected with the other end of a twelfth resistor; one end of the seventeenth capacitor is further connected to a negative input end of a sixth operational amplifier, a nineteenth resistor is further connected in parallel between the negative input end and the output end of the sixth operational amplifier, the positive input end of the sixth operational amplifier is further connected to one end of a twentieth resistor, one end of the twentieth resistor is further connected to one end of a twentieth capacitor, the other ends of the twentieth resistor and the twentieth capacitor are both grounded, one end of the twentieth capacitor is further connected to one end of a twenty-first resistor, the other end of the twenty-first resistor is further connected to one end of a twenty-first capacitor, the other end of the twenty-first capacitor is grounded, and one end of the twenty-first capacitor is further connected to a VCC power supply; the output end of the sixth operational amplifier is further connected with one end of a twenty-second capacitor, one end of the twenty-second capacitor is further connected with one end of a twenty-third capacitor, the other ends of the twenty-second capacitor and the twenty-third capacitor are both grounded, and one end of the twenty-third capacitor is further connected with an output port; the positive power supply terminal of the second operational amplifier is connected with a V + power supply, and the negative power supply terminal of the second operational amplifier is connected with a V-power supply; a positive power supply terminal of the fourth operational amplifier is connected with a V + power supply, and a negative power supply terminal of the fourth operational amplifier is connected with a V-power supply; a positive power supply terminal of the first operational amplifier is connected with one end of a fourth capacitor, the other end of the fourth capacitor is grounded, and one end of the fourth capacitor is also connected with a V + power supply; a negative power supply terminal of the first operational amplifier is connected with one end of a fifth capacitor, the other end of the fifth capacitor is grounded, and one end of the fifth capacitor is also connected with a V-power supply; a positive power supply terminal of the third operational amplifier is connected with one end of a tenth capacitor, the other end of the tenth capacitor is grounded, and one end of the tenth capacitor is also connected with a V + power supply; a negative power supply terminal of the third operational amplifier is connected with one end of a ninth capacitor, the other end of the ninth capacitor is grounded, and one end of the ninth capacitor is also connected with a V-power supply; a positive power supply terminal of the fifth operational amplifier is connected with one end of a sixteenth capacitor, the other end of the sixteenth capacitor is grounded, and one end of the sixteenth capacitor is also connected with a V + power supply; a negative power supply terminal of the fifth operational amplifier is connected with one end of a fifteenth capacitor, the other end of the fifteenth capacitor is grounded, and one end of the fifteenth capacitor is also connected with a V-power supply; a positive power supply terminal of the sixth operational amplifier is connected with one end of an eighteenth capacitor, the other end of the eighteenth capacitor is grounded, and one end of the eighteenth capacitor is also connected with a V + power supply; and a negative power supply terminal of the sixth operational amplifier is connected with one end of a nineteenth capacitor, the other end of the nineteenth capacitor is grounded, and one end of the nineteenth capacitor is also connected with a V-power supply.

The invention obtains good sensitivity through the cooperation of multistage operational amplifiers, filters mixed power supply frequency noise when amplifying weak signals, ensures the effectiveness and anti-interference of filtering, improves the Q value through the operational amplifiers and positive feedback to reduce the filtering loss and prevent electromagnetic interference; the frequency can be adjusted by a potentiometer to reduce the output voltage, thereby preventing the reduction of the resonant frequency caused by the dispersion of the capacitor.

The invention has the advantages that: 1) ensuring a high Q value, reducing the filtering loss of the high Q value and preventing electromagnetic interference; 2) the filtering effect meets the requirement, and the occurrence of interference is prevented; 3) the frequency is adjusted by the potentiometer to prevent the reduction of the resonance frequency due to the dispersion of the capacitance.

Drawings

Fig. 1 is a schematic circuit diagram of the present invention.

Detailed Description

The invention is further described with reference to the following drawings and detailed description.

Referring to fig. 1, a frequency filter circuit includes an input port Vin, an output port Vout, a first resistor R, a second resistor R, a third resistor R, a fourth resistor R, a fifth resistor R, a sixth resistor R, a seventh resistor R, an eighth resistor R, a ninth resistor R, a tenth resistor R, an eleventh resistor R, a twelfth resistor R, a thirteenth resistor R, a fourteenth resistor R, a fifteenth resistor R, a sixteenth resistor R, a seventeenth resistor R, an eighteenth resistor R, a nineteenth resistor R, a twentieth resistor R, a twenty-first resistor R, a first capacitor C, a second capacitor C, a third capacitor C, a fourth capacitor C, a fifth capacitor C, a sixth capacitor C, a seventh capacitor C, an eighth capacitor C, a ninth capacitor C, a tenth capacitor C, an eleventh capacitor C, a twelfth capacitor C, a thirteenth capacitor C, a fourteenth capacitor C, a fifteenth capacitor C, a fifth capacitor C, A sixteenth capacitor C16, a seventeenth capacitor C17, an eighteenth capacitor C18, a nineteenth capacitor C19, a twentieth capacitor C20, a twenty-first capacitor C21, a first potentiometer RW1, a second potentiometer RW2, a first triode Q1, a second triode Q2, a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4, a fifth operational amplifier U5, a sixth operational amplifier U6 and a VCC power supply; the input port Vin is connected with one end of a first resistor R1, the other end of the first resistor R1 is further connected to a collector of a first triode Q1, a second resistor R2 is connected in series between a base and an emitter of the first triode Q1, a collector of the first triode Q1 is further connected to a base of a second triode Q2, a base of the first triode Q1 is further connected to an emitter of the second triode Q2, a collector of the second triode Q2 is connected with one end of a first capacitor C1, one end of the first capacitor C1 is further connected to one end of a second capacitor C2, one end of the second capacitor C2 is further connected to one end of a third resistor R3, the other ends of the first capacitor C1, the second capacitor and the third resistor R3 are both grounded, one end of the third resistor R3 is further connected to a positive input end of a first operational amplifier U1, a negative input end of the first operational amplifier U1 is connected with one end of a fourth resistor R4, the other end of the fourth resistor R4 is connected to the output end of the first operational amplifier U1, the fourth resistor R4 is further connected in parallel with a third capacitor C3, the output end of the first operational amplifier U1 is connected to one end of a first potentiometer RW1, the other end of the first potentiometer RW1 is connected to an eighth resistor R8, the other end of the eighth resistor R8 is grounded, the output end of the first operational amplifier U1 is further connected to one end of a fifth resistor R5, the other end of the fifth resistor R5 is connected to one end of a sixth resistor R6, the other end of the sixth resistor R6 is connected to the positive input end of the second operational amplifier U2, the other end of the sixth resistor R6 is further connected to one end of an eighth capacitor C8, the other end of the eighth capacitor C8 is connected to one end of a sixth capacitor C6, the other end of the sixth capacitor C6 is connected to the variable resistance end of the first potentiometer 1, the other end of the eighth capacitor C8 is further connected to the seventh resistor RW 7, the other end of the seventh resistor R7 is connected to one end of a seventh capacitor C7, the other end of the seventh capacitor C7 is connected to one end of a sixth resistor R6, the negative input end of the second operational amplifier U2 is connected to the output end of the second operational amplifier U2, the output end of the second operational amplifier U2 is connected to one end of a ninth resistor R9, the other end of the seventh resistor R7 is further connected to the output end of the third operational amplifier U3, the output end of the third operational amplifier U3 is further connected to the negative input end of a third operational amplifier U3, the positive input end of the third operational amplifier U3 is connected to one end of a tenth resistor R10, the other end of the tenth resistor R10 is grounded, one end of the tenth resistor R10 is further connected to one end of an eleventh resistor R11, the other end of the eleventh resistor R11 is connected to one end of an eleventh capacitor C11, the other end of the ninth resistor R9 is also connected to one end of a seventh capacitor C11, and the other end of the eleventh capacitor C11 is grounded, one end of the eleventh capacitor C11 is further connected to one end of a thirteenth resistor R13, one end of the thirteenth resistor R13 is further connected to one end of a second potentiometer RW2, the other end of the second potentiometer RW2 is connected to one end of a fourteenth resistor R14, the other end of the thirteenth resistor R13 is connected to one end of a twelfth resistor R12, the other end of the twelfth resistor R12 is connected to one end of a fourteenth capacitor C14, the other end of the fourteenth capacitor C14 is connected to one end of a twelfth capacitor C12, the other end of the twelfth capacitor C12 is connected to a variable-resistance end of a second potentiometer RW2, the other end of the thirteenth resistor R13 is further connected to one end of a thirteenth capacitor C13, the other end of the thirteenth capacitor C13 is connected to one end of a fifteenth resistor R15, the other end of the fifteenth resistor R15 is connected to the other end of a fourteenth capacitor C14, one end of the fifteenth resistor R15 is further connected to an output end of a fifth operational amplifier U5, an output end of the fifth operational amplifier U5 is connected to a negative input end of a fifth operational amplifier U5, a positive input end of the fifth operational amplifier U5 is connected to one end of a seventeenth resistor R17, the other ends of the seventeenth resistor R17 and the fourteenth resistor R14 are both grounded, one end of the seventeenth resistor R17 is further connected to one end of an eighteenth resistor R18, the other end of the eighteenth resistor R18 is connected to one end of a seventeenth capacitor C17, the other end of the seventeenth capacitor C17 is grounded, one end of the seventeenth capacitor C17 is further connected to one end of a sixteenth resistor R16, the other end of the sixteenth resistor R16 is connected to an output end of a fourth operational amplifier U4, an output end of the fourth operational amplifier U4 is connected to a negative input end of a fourth operational amplifier U4, and a positive input end of the fourth operational amplifier U4 is connected to the other end of a twelfth resistor R12; one end of the seventeenth capacitor C17 is further connected to a negative input end of a sixth operational amplifier U6, a nineteenth resistor R19 is further connected in parallel between the negative input end and the output end of the sixth operational amplifier U6, the positive input end of the sixth operational amplifier U6 is further connected to one end of a twentieth resistor R20, one end of the twentieth resistor R20 is further connected to one end of a twentieth capacitor C20, the other ends of the twentieth resistor R20 and the twentieth capacitor C20 are both grounded, one end of the twentieth capacitor C20 is further connected to one end of a twenty-first resistor R21, the other end of the twenty-first resistor R21 is further connected to one end of a twenty-first capacitor C21, the other end of the twenty-first capacitor C21 is grounded, and one end of the twenty-first capacitor C21 is further connected to a VCC power supply; the output end of the sixth operational amplifier U6 is further connected to one end of a twenty-second capacitor C22, one end of the twenty-second capacitor C22 is further connected to one end of a twenty-third capacitor C23, the other ends of the twenty-second capacitor C22 and the twenty-third capacitor C23 are both grounded, and one end of the twenty-third capacitor C23 is further connected to the output port Vout; the positive power supply terminal of the second operational amplifier U2 is connected with a V + power supply, and the negative power supply terminal of the second operational amplifier U2 is connected with a V-power supply; the positive power supply terminal of the fourth operational amplifier U4 is connected with a V + power supply, and the negative power supply terminal of the fourth operational amplifier U4 is connected with a V-power supply; the positive power supply terminal of the first operational amplifier U1 is connected with one end of a fourth capacitor C4, the other end of the fourth capacitor C4 is grounded, and one end of the fourth capacitor C4 is also connected with a V + power supply; the negative power supply terminal of the first operational amplifier U1 is connected with one end of a fifth capacitor C5, the other end of the fifth capacitor C5 is grounded, and one end of the fifth capacitor C5 is also connected with a V-power supply; the positive power supply terminal of the third operational amplifier U3 is connected with one end of a tenth capacitor C10, the other end of the tenth capacitor C10 is grounded, and one end of the tenth capacitor C10 is also connected with a V + power supply; the negative power supply terminal of the third operational amplifier U3 is connected with one end of a ninth capacitor C9, the other end of the ninth capacitor C9 is grounded, and one end of the ninth capacitor C9 is also connected with a V-power supply; the positive power supply terminal of the fifth operational amplifier U5 is connected with one end of a sixteenth capacitor C16, the other end of the sixteenth capacitor C16 is grounded, and one end of the sixteenth capacitor C16 is also connected with a V + power supply; the negative power supply terminal of the fifth operational amplifier U5 is connected with one end of a fifteenth capacitor C15, the other end of the fifteenth capacitor C15 is grounded, and one end of the fifteenth capacitor C15 is also connected with a V-power supply; the positive power supply terminal of the sixth operational amplifier U6 is connected with one end of an eighteenth capacitor C18, the other end of the eighteenth capacitor C18 is grounded, and one end of the eighteenth capacitor C18 is also connected with a V + power supply; the negative power supply terminal of the sixth operational amplifier U6 is connected with one end of a nineteenth capacitor C19, the other end of the nineteenth capacitor C19 is grounded, and one end of the nineteenth capacitor C19 is also connected with a V-power supply.

In this embodiment, the Q value of the whole circuit is increased by combining a plurality of operational amplifiers and a positive feedback circuit, and after the 55Hz power frequency, i.e. the sinusoidal voltage, is input, the first potentiometer RW1 and the second potentiometer RW2 are adjusted to reduce the output voltage of the whole filter circuit, so as to prevent the reduction of the resonant frequency, and then the noise of the power frequency is filtered out by filtering with a multi-stage operational amplifier.

The scope of the present invention includes, but is not limited to, the above embodiments, and the present invention is defined by the appended claims, and any alterations, modifications, and improvements that may occur to those skilled in the art are all within the scope of the present invention.

Claims

1. A frequency filter circuit, characterized by: the high-voltage power supply comprises an input port (Vin), an output port (Vout), a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a sixth resistor (R6), a seventh resistor (R7), an eighth resistor (R8), a ninth resistor (R9), a tenth resistor (R10), an eleventh resistor (R11), a twelfth resistor (R12), a thirteenth resistor (R13), a fourteenth resistor (R13), a fifteenth resistor (R13), a sixteenth resistor (R13), a seventeenth resistor (R13), an eighteenth resistor (R13), a nineteenth resistor (R13), a twentieth resistor (R13), a twenty-first resistor (R13), a first capacitor (C13), a second capacitor (C13), a third capacitor (C13), a fourth capacitor (C13), a fifth capacitor (C13), a sixth capacitor (C13), an eighth capacitor (C13), and an eighth capacitor (C13), A ninth capacitor (C9), a tenth capacitor (C10), an eleventh capacitor (C11), a twelfth capacitor (C12), a thirteenth capacitor (C13), a fourteenth capacitor (C14), a fifteenth capacitor (C15), a sixteenth capacitor (C16), a seventeenth capacitor (C17), an eighteenth capacitor (C18), a nineteenth capacitor (C19), a twentieth capacitor (C20), a twenty-first capacitor (C21), a first potentiometer (RW 1), a second potentiometer (RW 2), a first triode (Q1), a second triode (Q2), a first operational amplifier (U1), a second operational amplifier (U2), a third operational amplifier (U3), a fourth operational amplifier (U4), a fifth operational amplifier (U5), a sixth operational amplifier (U6), and a VCC power supply; the input port (Vin) is connected with one end of a first resistor (R1), the other end of the first resistor (R1) is further connected with a collector of a first triode (Q1), a second resistor (R2) is connected in series between a base and an emitter of the first triode (Q1), the collector of the first triode (Q1) is further connected with a base of a second triode (Q2), the base of the first triode (Q1) is further connected with an emitter of a second triode (Q2), the collector of the second triode (Q2) is connected with one end of a first capacitor (387C 1), one end of the first capacitor (C1) is further connected with one end of a second capacitor (C2), one end of the second capacitor (C2) is further connected with one end of a third resistor (R3), the first capacitor (C1) and the second capacitor and the other end of the third resistor (R3) are grounded, and one end of the third resistor (R3) is further connected with a positive input terminal (U1), the negative input end of the first operational amplifier (U1) is connected with one end of a fourth resistor (R4), the other end of the fourth resistor (R4) is connected with the output end of the first operational amplifier (U1), the fourth resistor (R4) is also connected with a third capacitor (C3) in parallel, the output end of the first operational amplifier (U1) is connected with one end of a first potentiometer (RW 1), the other end of the first potentiometer (RW 1) is connected with an eighth resistor (R8), the other end of the eighth resistor (R8) is grounded, the output end of the first operational amplifier (U1) is also connected with one end of a fifth resistor (R5), the other end of the fifth resistor (R5) is connected with one end of a sixth resistor (R6), the other end of the sixth resistor (R6) is connected with the positive input end of the second operational amplifier (U2), the other end of the sixth resistor (R6) is also connected with one end of an eighth capacitor (C4642), and the other end of the sixth capacitor (C6) is connected with the first end of the eighth capacitor (C6), the other end of the sixth capacitor (C6) is connected to the resistance-changing end of the first potentiometer (RW 1), the other end of the eighth capacitor (C8) is further connected to one end of a seventh resistor (R7), the other end of the seventh resistor (R7) is connected to one end of a seventh capacitor (C7), the other end of the seventh capacitor (C7) is connected to one end of a sixth resistor (R6), the negative input end of the second operational amplifier (U2) is connected to the output end of the second operational amplifier (U2), the output end of the second operational amplifier (U2) is connected to one end of a ninth resistor (R9), the other end of the seventh resistor (R7) is further connected to the output end of a third operational amplifier (U3), the output end of the third operational amplifier (U3) is further connected to the negative input end of a third operational amplifier (U3), the positive input end of the third operational amplifier (U3) is connected to the tenth end of a resistor (R10), and the other end of the resistor (R10) is grounded, one end of the tenth resistor (R10) is further connected with one end of an eleventh resistor (R11), the other end of the eleventh resistor (R11) is connected with one end of an eleventh capacitor (C11), the other end of the ninth resistor (R9) is also connected with one end of an eleventh capacitor (C11), the other end of the eleventh capacitor (C11) is grounded, one end of the eleventh capacitor (C11) is further connected with one end of a thirteenth resistor (R13), one end of the thirteenth resistor (R13) is further connected with one end of a second potentiometer (RW 2), the other end of the second potentiometer (RW 2) is connected with one end of a fourteenth resistor (R14), the other end of the thirteenth resistor (R13) is connected with one end of a twelfth resistor (R12), the other end of the twelfth resistor (R12) is connected with one end of a fourteenth capacitor (C14), and the other end of the fourteenth capacitor (C14) is connected with one end of a twelfth capacitor (C12), the other end of the twelfth capacitor (C12) is connected to the resistance-changing end of the second potentiometer (RW 2), the other end of the thirteenth resistor (R13) is further connected to one end of a thirteenth capacitor (C13), the other end of the thirteenth capacitor (C13) is connected to one end of a fifteenth resistor (R15), the other end of the fifteenth resistor (R15) is connected to the other end of the fourteenth capacitor (C14), one end of the fifteenth resistor (R15) is further connected to the output end of a fifth operational amplifier (U5), the output end of the fifth operational amplifier (U5) is connected to the negative input end of a fifth operational amplifier (U5), the positive input end of the fifth operational amplifier (U5) is connected to one end of a seventeenth resistor (R17), the other ends of the seventeenth resistor (R17) and the fourteenth resistor (R14) are both grounded, one end of the seventeenth resistor (R17) is further connected to the eighteenth resistor (R18), the other end of the eighteenth resistor (R18) is connected with one end of a seventeenth capacitor (C17), the other end of the seventeenth capacitor (C17) is grounded, one end of the seventeenth capacitor (C17) is also connected with one end of a sixteenth resistor (R16), the other end of the sixteenth resistor (R16) is connected with the output end of a fourth operational amplifier (U4), the output end of the fourth operational amplifier (U4) is connected with the negative input end of the fourth operational amplifier (U4), and the positive input end of the fourth operational amplifier (U4) is connected with the other end of a twelfth resistor (R12); one end of the seventeenth capacitor (C17) is further connected to a negative input end of a sixth operational amplifier (U6), a nineteenth resistor (R19) is further connected in parallel between the negative input end and the output end of the sixth operational amplifier (U6), the positive input end of the sixth operational amplifier (U6) is further connected to one end of a twentieth resistor (R20), one end of the twentieth resistor (R20) is further connected to one end of a twentieth capacitor (C20), the twentieth resistor (R20) and the twentieth capacitor (C20) are both grounded, one end of the twentieth capacitor (C20) is further connected to one end of a twenty-first resistor (R21), the other end of the twenty-first resistor (R21) is further connected to one end of a twenty-first capacitor (C21), the other end of the twenty-first capacitor (C21) is grounded, and one end of the twenty-first capacitor (C21) is further connected to a VCC power supply; the output end of the sixth operational amplifier (U6) is further connected with one end of a twenty-second capacitor (C22), one end of the twenty-second capacitor (C22) is further connected with one end of a twenty-third capacitor (C23), the other ends of the twenty-second capacitor (C22) and the twenty-third capacitor (C23) are grounded, and one end of the twenty-third capacitor (C23) is further connected with an output port (Vout).

2. A frequency filter circuit according to claim 1, wherein: the positive power supply terminal of the second operational amplifier (U2) is connected with a V + power supply, and the negative power supply terminal of the second operational amplifier (U2) is connected with a V-power supply; the positive power supply terminal of the fourth operational amplifier (U4) is connected to a V + power supply, and the negative power supply terminal of the fourth operational amplifier (U4) is connected to a V-power supply.

3. A frequency filter circuit according to claim 1, wherein: the positive power supply terminal of the first operational amplifier (U1) is connected with one end of a fourth capacitor (C4), the other end of the fourth capacitor (C4) is grounded, and one end of the fourth capacitor (C4) is also connected with a V + power supply; the negative power supply terminal of the first operational amplifier (U1) is connected with one end of a fifth capacitor (C5), the other end of the fifth capacitor (C5) is grounded, and one end of the fifth capacitor (C5) is also connected with a V-power supply; the positive power supply terminal of the third operational amplifier (U3) is connected with one end of a tenth capacitor (C10), the other end of the tenth capacitor (C10) is grounded, and one end of the tenth capacitor (C10) is also connected with a V + power supply; the negative power supply terminal of the third operational amplifier (U3) is connected with one end of a ninth capacitor (C9), the other end of the ninth capacitor (C9) is grounded, and one end of the ninth capacitor (C9) is also connected with a V-power supply; the positive power supply terminal of the fifth operational amplifier (U5) is connected with one end of a sixteenth capacitor (C16), the other end of the sixteenth capacitor (C16) is grounded, and one end of the sixteenth capacitor (C16) is also connected with a V + power supply; the negative power supply terminal of the fifth operational amplifier (U5) is connected with one end of a fifteenth capacitor (C15), the other end of the fifteenth capacitor (C15) is grounded, and one end of the fifteenth capacitor (C15) is also connected with a V-power supply; the positive power supply terminal of the sixth operational amplifier (U6) is connected with one end of an eighteenth capacitor (C18), the other end of the eighteenth capacitor (C18) is grounded, and one end of the eighteenth capacitor (C18) is also connected with a V + power supply; the negative power supply terminal of the sixth operational amplifier (U6) is connected with one end of a nineteenth capacitor (C19), the other end of the nineteenth capacitor (C19) is grounded, and one end of the nineteenth capacitor (C19) is also connected with a V-power supply.