CN215493969U

CN215493969U - Characteristic testing device for amplifying circuit

Info

Publication number: CN215493969U
Application number: CN202121592863.4U
Authority: CN
Inventors: 蒋燕君; 孔丽萍; 谷嘉炜; 许程涛; 蒋汉聂; 周凌宜; 王鑫挺; 杨鸿伟; 夏榕欣
Original assignee: Zhejiang Shuren University
Current assignee: Zhejiang Shuren University
Priority date: 2021-07-13
Filing date: 2021-07-13
Publication date: 2022-01-11
Anticipated expiration: 2031-07-13

Abstract

The utility model provides an amplifier circuit characteristic test device, including the signal source input resistance switching circuit that is used for controlling signal source input resistance value, a first voltage follower that is used for isolating and eliminating impedance influence between preceding stage circuit and back stage circuit, an amplifier circuit that is used for amplifying sinusoidal wave input signal, a first true virtual value converting circuit that is used for measuring sinusoidal signal true virtual value, an auxiliary power circuit that is used for providing the power, a load resistance switching circuit that is used for controlling load resistance value, a second voltage follower that is used for isolating and eliminating impedance influence between preceding stage circuit and back stage circuit, a second true virtual value converting circuit that is used for measuring sinusoidal signal true virtual value, a keying circuit that is used for realizing resetting and switching the measuring variable, a display circuit and a microprocessor MCU that are used for showing the measuring value. The utility model provides a device for testing the characteristics of an amplifying circuit, which judges the characteristics of the amplifying circuit by changing the access states of input and output end elements, and has the advantages of low cost, high data precision, convenient operation and high practicability.

Description

Characteristic testing device for amplifying circuit

Technical Field

The utility model relates to the technical field of integrated circuit testing, in particular to an amplifying circuit characteristic testing device.

Background

The explosive development of the integrated circuit industry is not free from circuit testing techniques. The circuit test can effectively verify the rationality of the circuit design, monitor the quality of an integrated circuit in the processing process, analyze effective data of the integrated circuit and help designers to upgrade the circuit design scheme. The traditional circuit performance test steps are complicated, more instruments need to be used, inconvenience is brought to test experiments due to different precision of experimental instruments, and manual multiple measurement and data recording are needed. At present, circuit test systems are developing towards automation and intellectualization, which requires that the circuit test systems automatically measure and process circuit characteristic data and output circuit characteristic test results in a proper manner with little involvement of technicians. The amplifier circuit is used as an important circuit for enhancing signal amplitude or signal power, and is widely applied to devices such as communication, radar, broadcasting and the like, and the basic characteristics of the amplifier circuit are represented in three indexes of input resistance, output resistance and voltage gain.

Disclosure of Invention

In order to overcome the defects in the prior art, the utility model provides the amplifying circuit characteristic testing device, which judges the characteristics of the amplifying circuit by changing the access states of the input end element and the output end element, and has the advantages of low cost, high data precision and high practicability.

The design scheme adopted by the utility model for the realized test circuit characteristics is as follows:

a kind of amplifying circuit characteristic test device, including the signal source input resistance switching circuit used for controlling the input resistance value of the signal source, the first voltage follower used for isolating and eliminating the impedance influence between the front and back circuit, the amplifying circuit used for amplifying the sine wave input signal, the first true effective value switching circuit used for measuring the true effective value of the sine signal, the auxiliary power circuit used for providing the power, the load resistance switching circuit used for controlling the load resistance value, the second voltage follower used for isolating and eliminating the impedance influence between the front and back circuit, the second true effective value switching circuit used for measuring the true effective value of the sine signal, the key circuit used for realizing resetting and switching the test quantity, the display circuit used for displaying the measured value and the microprocessor MCU;

the signal source input resistance switching circuit is respectively connected with an IO1, a first voltage follower and an input end of a circuit to be tested of the microprocessor MCU, the auxiliary power circuit is respectively connected with a 12V direct current, the signal source input resistance switching circuit, the first voltage follower, an amplifying circuit, a first true effective value conversion circuit, a key circuit, a display circuit, a load resistance switching circuit, a second voltage follower and a second true effective value conversion circuit, the first voltage follower is connected with the amplifying circuit, the amplifying circuit is connected with the first true effective value conversion circuit, the first true effective value conversion circuit is connected with an AD1 of the microprocessor MCU, the key circuit is connected with a RESET of the microprocessor MCU and an IO5 of the microprocessor MCU, the display circuit is connected with the IO3 of the microprocessor MCU and the IO4 of the microprocessor MCU, and the load resistance switching circuit is respectively connected with an IO2 of the MCU microprocessor, The output end of the circuit to be tested is connected, the second voltage follower is connected with the output end of the circuit to be tested and the second true effective value conversion circuit, and the second true effective value conversion circuit is connected with the AD2 of the microprocessor MCU.

Further, the signal source input resistance switching circuit comprises a first resistor, a second resistor, a third resistor, a first diode, a first triode and a first relay.

An end connection microprocessor MCU's IO1 of second resistance, the other end of second resistance with the base of first triode is connected, the negative pole of first diode respectively with power +5V the 4 feet of first relay are connected, the positive pole of first diode with the one end of first resistance is connected, the other end of first resistance simultaneously with the collecting electrode of first triode, the 5 feet of first relay are connected, the projecting pole of first triode connects power ground GND, 1 foot of first relay connects the circuit input that awaits measuring, 3 feet of first relay with the one end of third resistance is connected, the other end of third resistance, 2 feet of first relay simultaneously with the homophase end of the first fortune of first voltage follower is put is connected.

Still further, the first voltage follower includes a first operational amplifier and a first capacitor.

The inverting terminal of the first operational amplifier is respectively connected with the output terminal of the first operational amplifier and one end of a first capacitor, the power supply terminal of the first operational amplifier is connected with a +12V power supply, the grounding terminal of the first operational amplifier is connected with a power supply ground GND, and the other end of the first capacitor is connected with one end of a fourth resistor of the amplifying circuit.

Still further, the amplifying circuit comprises a fourth resistor, a fifth resistor, a sixth resistor and a second operational amplifier.

The other end of the fourth resistor is connected with one end of the fifth resistor and the inverting end of the second operational amplifier respectively, the in-phase end of the second operational amplifier is connected with one end of the sixth resistor, the other end of the sixth resistor is connected with a power ground GND, the ground end of the second operational amplifier is connected with a-5V power supply, the power end of the second operational amplifier is connected with a +5V power supply, and the output end of the second operational amplifier and the other end of the fifth resistor are connected with one end of the twelfth resistor of the first true effective value conversion circuit and the 3 pins of the second interface simultaneously.

Still further, the first true effective value conversion circuit includes 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 second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a second diode, a third diode, a fourth diode, a fifth diode, a first sliding rheostat, a first interface, a second interface, and a first true effective value conversion chip.

The cathode of the fourth diode is connected with a power supply ground GND, the anode of the fourth diode is connected with one end of a ninth resistor, the other end of the ninth resistor, one end of a seventh resistor and the cathode of a second diode are simultaneously connected with a + VS power supply, the other end of the seventh resistor and the anode of a second capacitor are simultaneously connected with a + VA power supply, the cathode of the second capacitor is connected with the power supply ground GND, the anode of the second diode and the pin 1 of the first interface are simultaneously connected with a +5V power supply, the pin 2 of the first interface is connected with the power supply ground GND, the pin 3 of the first interface and the cathode of a third diode are simultaneously connected with a-5V power supply, the anode of the third diode, one end of an eighth resistor and one end of a tenth resistor are simultaneously connected with the-VS power supply, the other end of the eighth resistor and the cathode of the third capacitor are simultaneously connected with the-VA power supply, the anode of the third capacitor is connected with a power ground GND, the other end of the tenth resistor is connected with the cathode of the fifth diode, the anode of the fifth diode is connected with the power ground GND, the 6-pin and one end of the seventeenth resistor of the second interface are simultaneously connected with an AD1 of the microprocessor MCU, the 4-pin and the 5-pin of the second interface are simultaneously connected with the power ground GND, the 3-pin of the second interface is connected with one end of the twelfth resistor, the 2-pin of the second interface is connected with the power ground GND, the 1-pin of the second interface is connected with one end of the eighteenth resistor, the 3-pin of the first slide rheostat is connected with a-VA power supply, the 1-pin of the first slide rheostat is connected with a + VA power supply, the 2-pin of the first slide rheostat is connected with one end of the eleventh resistor, the 1-pin of the first true effective value conversion chip is simultaneously connected with one end of the fifteenth resistor and one end of the fourth capacitor, the other end of the fourth capacitor is connected with a power ground GND, 4 pins of the first true effective value conversion chip are connected with the other end of the eleventh resistor, 15 pins of the first true effective value conversion chip are connected with one end of the fifth capacitor, the other end of the fifth capacitor is connected with the other end of the twelfth resistor and one end of the thirteenth resistor, the other end of the thirteenth resistor is connected with the power ground GND, 5 pins of the first true effective value conversion chip are connected with one end of the fourteenth resistor, the other end of the fourteenth resistor is connected with a VA power supply, 2 pins, 7 pins, 8 pins, 9 pins and 14 pins of the first true effective value conversion chip are suspended, 6 pins and 11 pins of the first true effective value conversion chip are connected with one end of the sixteenth resistor, the other end of the seventeenth resistor and one end of the eighth capacitor, 13 pins, 11 pins of the first true effective value conversion chip, and the other end of the eleventh resistor are connected with the other end of the eleventh resistor and one end of the thirteenth resistor, and the thirteenth resistor, One end of a sixth capacitor is connected with a VA power supply at the same time, the other end of the sixth capacitor is connected with a power supply ground GND, 16 pins of a first true effective value conversion chip are respectively connected with the other end of an eighteenth resistor and one end of a ninth capacitor, 10 pins of the first true effective value conversion chip are connected with the other end of the eighth capacitor, 12 pins of the first true effective value conversion chip and one end of a seventh capacitor are connected with a VA power supply at the same time, 3 pins of the first true effective value conversion chip and the other end of the seventh capacitor are connected with the power supply ground GND at the same time, and the other end of a fifteenth resistor is connected with the other end of the sixteenth resistor and the other end of the ninth capacitor at the same time.

Still further, the auxiliary power supply circuit comprises a third interface and an isolation power supply module;

the power supply comprises a third interface, a power supply ground GND, an isolation power supply module, a power supply ground GND, a power supply ground 5 and a power supply ground 5, wherein the power supply ground GND is connected with the power supply ground 2 pins of the third interface, the power supply ground GND is connected with the power supply ground 5 pins of the isolation power supply module, and the power supply ground 5 pins of the isolation power supply module are connected with the power supply ground 6 pins of the isolation power supply module.

Still further, the load resistance switching circuit includes a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a sixth diode, a second triode, and a second relay.

An end of twentieth resistance connects microprocessor MCU's IO2, the other end of twentieth resistance with the base of second triode is connected, the negative pole of sixth diode, 4 feet of second relay connect +5V power simultaneously, the positive pole of sixth diode with the one end of nineteenth resistance is connected, the other end of nineteenth resistance, 5 feet of second relay are connected with the collecting electrode of second triode simultaneously, the projecting pole of second triode, the one end of twenty-first resistance connect power ground GND simultaneously, 1 foot of second relay with the one end of the tenth electric capacity of second voltage follower connects circuit output end simultaneously, 3 feet of second relay with the other end of twenty-first resistance is connected, 2 feet of second relay are unsettled.

Still further, the second voltage follower comprises a tenth capacitor and a third operational amplifier;

the in-phase end of the third operational amplifier is connected with the other end of the tenth capacitor, the inverting end and the output end of the third operational amplifier are simultaneously connected with the pin 3 of the fifth interface of the second true effective value conversion circuit and one end of the twenty-seventh resistor, the power supply end of the third operational amplifier is connected with a +12V power supply, and the grounding end of the third operational amplifier is connected with a power supply ground GND.

Still further, the second true effective value conversion circuit includes a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, a twenty-sixth resistor, a twenty-seventh resistor, a twenty-eighth resistor, a twenty-ninth resistor, a thirty-third resistor, a thirty-eleventh resistor, a thirty-second resistor, a thirty-third resistor, 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 seventh diode, an eighth diode, a ninth diode, a twelfth diode, a second slide rheostat, a fourth interface, a fifth interface, and a second true effective value conversion chip.

The cathode of the ninth diode is connected with a power supply ground GND, the anode of the ninth diode is connected with one end of a twenty-fourth resistor, the other end of the twenty-fourth resistor, one end of a twenty-second resistor and the cathode of a seventh diode are simultaneously connected with a + VS power supply, the other end of the twenty-second resistor and the anode of an eleventh capacitor are simultaneously connected with a + VA power supply, the cathode of the eleventh capacitor is connected with the power supply ground GND, the anode of the seventh diode and a pin 1 of a fourth interface are simultaneously connected with a +5V power supply, a pin 2 of the fourth interface is connected with the power supply ground GND, a pin 3 of the fourth interface and a cathode of an eighth diode are connected with a-5V power supply, the anode of the eighth diode, one end of the twenty-third resistor and one end of a twenty-fifth resistor are simultaneously connected with a-VS power supply, and the other end of the twenty-third resistor, The negative electrode of a twelfth capacitor is simultaneously connected with a-VA power supply, the positive electrode of the twelfth capacitor is connected with a power supply ground GND, the other end of the twenty-fifth resistor is connected with the cathode of the twelfth diode, the anode of the twelfth diode is connected with the power supply ground GND, one ends of a 6 pin of the fifth interface and a thirty-second resistor are simultaneously connected with an AD2 of the microprocessor MCU, 4 pins and 5 pins of the fifth interface are simultaneously connected with the power supply ground GND, a 2 pin of the fifth interface is connected with the power supply ground GND, a1 pin of the fifth interface is connected with one end of the thirty-third resistor, a 3 pin of the second slide rheostat is connected with the-VA power supply, a1 pin of the second slide rheostat is connected with the + VA power supply, a 2 pin of the second slide rheostat is connected with one end of the twenty-sixth resistor, a1 pin of the second true effective value conversion chip is simultaneously connected with one end of the thirty-resistor, One end of a thirteenth capacitor is connected, the other end of the thirteenth capacitor is connected with a power supply ground GND, 4 pins of a second true effective value conversion chip are connected with the other end of a twenty-sixth resistor, 15 pins of the second true effective value conversion chip are connected with one end of a fourteenth capacitor, the other end of a twenty-seventh resistor is connected with the other end of the fourteenth capacitor and one end of a twenty-eighth resistor, the other end of the twenty-eighth resistor is connected with the power supply ground GND, 5 pins of the second true effective value conversion chip are connected with one end of a twenty-ninth resistor, the other end of the twenty-ninth resistor is connected with a VA power supply, 2 pins, 7 pins, 8 pins, 9 pins and 14 pins of the second true effective value conversion chip are suspended, and 6 pins and 11 pins of the second true effective value conversion chip are connected with one end of a thirty-first resistor and the other end of a thirty-second resistor, One end of a seventeenth capacitor is connected, one end of a 13 pin and one end of a fifteenth capacitor of the second true effective value conversion chip are connected with a + VA power supply, the other end of the fifteenth capacitor is connected with a power supply ground GND, a 16 pin of the second true effective value conversion chip is respectively connected with the other end of a thirty-third resistor and one end of an eighteenth capacitor, a 10 pin of the second true effective value conversion chip is connected with the other end of the seventeenth capacitor, one end of a12 pin and one end of a sixteenth capacitor of the second true effective value conversion chip are connected with the-VA power supply, the other end of a 3 pin and the other end of a sixteenth capacitor of the second true effective value conversion chip are connected with the power supply ground GND, and the other end of the thirty resistor is connected with the other end of a thirty-first resistor and the other end of the eighteenth capacitor.

Furthermore, the key circuit comprises a thirty-fourth resistor, a thirty-fifth resistor, a nineteenth capacitor, a twentieth capacitor, a first key switch and a second key switch;

one end of the thirty-fourth resistor is connected with a +5V power supply, the other end of the thirty-fourth resistor, one end of the first key switch and one end of the nineteenth capacitor are simultaneously connected with a RESET of the microprocessor MCU, the other end of the first key switch and the other end of the nineteenth capacitor are simultaneously connected with a power supply ground GND, one end of the thirty-fifth resistor is connected with the +5V power supply, the other end of the thirty-fifth resistor, one end of the second key switch and one end of the twentieth capacitor are simultaneously connected with an IO5 of the microprocessor MCU, and the other end of the second key switch and the other end of the twentieth capacitor are simultaneously connected with the power supply ground GND;

the display circuit comprises a thirty-sixth resistor, a thirty-seventh resistor, a thirty-eighth resistor, a third triode, a twenty-first capacitor, a twenty-second capacitor, a twenty-third capacitor, a twenty-fourth capacitor, a twenty-fifth capacitor, a twenty-sixth capacitor, a sixth interface and an OLED display;

the 1 pin of the sixth interface is connected with the 1 pin of the OLED display, the 2 pin of the sixth interface, one end of a thirty-sixth resistor, one end of a thirty-seventh resistor, one end of a twenty-first capacitor and the collector of a third triode are simultaneously connected with a +5V power supply, the 3 pins of the sixth interface are respectively connected with the other end of the thirty-sixth resistor and the 18 pins of the OLED display, the 4 pins of the sixth interface are respectively connected with the other end of the thirty-seventh resistor and the 19 pins of the OLED display, the 5 pins of the sixth interface are connected with the 14 pins of the OLED display, the 6 pins of the sixth interface are connected with the 15 pins of the OLED display, the 7 pins of the sixth interface are connected with the 13 pins of the OLED display, the 2 pins of the OLED display are connected with one end of the twenty-fifth capacitor, and the 3 pins of the OLED display are connected with the other end of the twenty-fifth capacitor, the 4 feet of the OLED display are connected with one end of the twenty-six capacitor, the 5 feet of the OLED display are connected with the other end of the twenty-six capacitor, the 6 feet and the 9 feet of the OLED display are simultaneously connected with an emitting electrode of a third triode, the 7 feet of the OLED display are suspended, the 8 feet, the 10 feet, the 11 feet, the 12 feet, the 16 feet, the 17 feet, the 20 feet, the 21 feet, the 22 feet, the 23 feet, the 24 feet, the 25 feet, the 29 feet and the 30 feet of the OLED display are simultaneously connected with the other end of a twenty-first capacitor, the base electrode of a third triode, one end of a thirty-eighth resistor, one end of a twenty-second capacitor, one end of a twenty-third capacitor and one end of a twenty-fourth capacitor and are connected to a power ground GND, the 26 feet of the OLED display are connected with the other end of a thirty-eighth resistor, the 27 feet of the OLED display are connected with the other end of the twenty-fourth capacitor, and the pin 28 of the OLED display is simultaneously connected with the other end of the twenty-second capacitor and the other end of the twenty-third capacitor.

The utility model has the beneficial effects that:

the characteristic testing device of the amplifying circuit designed by the utility model adopts a method that a microprocessor controls the action of a relay to control and switch the access states of a signal source input resistor and a load resistor, and obtains the basic characteristic technical index of the amplifying circuit to be tested by measuring the input voltage and the output voltage in different access states; the characteristics of high input impedance and low output impedance of the first voltage follower and the second voltage follower are utilized to isolate and eliminate the influence on the amplifying circuit to be tested caused by the access of the amplifying circuit characteristic testing device; because the amplitude of the sine input signal used for testing is very small, an amplifying circuit is adopted in the testing device to amplify the input signal; the method comprises the steps that an alternating current voltage signal is converted into a direct current voltage signal by adopting a first true effective value conversion circuit and a second true effective value conversion circuit, the amplitude of the direct current voltage signal is equal to the effective value of the alternating current voltage signal, the first true effective value conversion circuit and the second true effective value conversion circuit both adopt high-precision AD637 chips and transmit the direct current voltage signal to an AD port of a microprocessor for sampling; the auxiliary power supply circuit is adopted to realize the power supply of the signal source input resistance switching circuit, the load resistance switching circuit, the first voltage follower, the second voltage follower, the amplifying circuit, the first true effective value conversion circuit, the second true effective value conversion circuit, the key circuit and the display circuit, and the used isolation power supply module A1205S-2W has stable performance and strong reliability, can convert 12V direct current voltage into +/-5V direct current voltage, is electrically isolated from the two and has high safety; the switching between display indexes and the resetting of a system are realized by adopting a key circuit, the input resistance value, the output resistance value and the voltage gain of the amplifying circuit to be tested are respectively and sequentially displayed by pressing a CHOOSE key each time, and the system is RESET when a RESET key is pressed; the OLED display screen is adopted to display three characteristic indexes of the amplifying circuit to be tested, the OLED display screen does not need a backlight source, the reaction speed is high, the contrast is high, and the display effect is good.

Drawings

Fig. 1 is an electrical schematic of the present invention.

Fig. 2 is a circuit diagram of a signal source input resistance switching circuit of the present invention.

Fig. 3 is a circuit diagram of a first voltage follower of the present invention.

Fig. 4 is a circuit diagram of an amplifier circuit of the present invention.

Fig. 5 is a circuit diagram of a first true significance conversion circuit of the present invention.

Fig. 6 is a circuit diagram of an auxiliary power supply circuit of the present invention.

Fig. 7 is a circuit diagram of a load resistance switching circuit of the present invention.

Fig. 8 is a circuit diagram of a second voltage follower of the present invention.

Fig. 9 is a circuit diagram of a second true significance conversion circuit of the present invention.

Fig. 10 is a circuit diagram of a key circuit of the present invention.

Fig. 11 is a circuit diagram of a display circuit of the present invention.

Detailed Description

The utility model is further described below with reference to the accompanying drawings.

As shown in FIG. 1, an amplifier circuit characteristic testing apparatus includes a signal source input resistance switching circuit for controlling a signal source input resistance value, a first voltage follower for isolating and eliminating an impedance influence between a front stage circuit and a rear stage circuit, an amplifier circuit for amplifying a sine wave input signal, a first true effective value conversion circuit for measuring a true effective value of a sine signal, an auxiliary power circuit for supplying power to the signal source input resistance switching circuit and the load resistance switching circuit, the amplifier circuit, the first voltage follower, the second voltage follower, the first true effective value conversion circuit and the second true effective value conversion circuit, a load resistance switching circuit for controlling a load resistance value, a second voltage follower for isolating and eliminating an impedance influence between the front stage circuit and the rear stage circuit, a second true effective value conversion circuit for measuring a true effective value of a sine signal, a first true effective value conversion circuit for measuring a true effective value of a sine signal, a second true effective value conversion circuit for measuring an impedance influence between the front stage circuit and the rear stage circuit, a second true effective value conversion circuit for measuring an impedance influence between the front stage circuit and rear stage circuit and the front stage circuit and the rear stage circuit, The device comprises a key circuit for resetting and switching test quantity, a display circuit for displaying a measured value and a microprocessor MCU (microprogrammed control Unit); the signal source input resistance switching circuit is respectively connected with an I01 (MCU _ IO 1), a first voltage follower and an input end of a circuit to be tested of the microprocessor MCU, the auxiliary power circuit is respectively connected with a 12V direct current, the signal source input resistance switching circuit, the first voltage follower, an amplifying circuit, a first true effective value converting circuit, a key circuit, a display circuit, a load resistance switching circuit, a second voltage follower and a second true effective value converting circuit, the first voltage follower is connected with the amplifying circuit, the amplifying circuit is connected with the first true effective value converting circuit, the first true effective value converting circuit is connected with an AD1 (MCU _ AD 1) of the microprocessing MCU, the key circuit is connected with a RESET (MCU _ RESET) of the microprocessor MCU and an IO5 (MCU _ IO 5) of the microprocessor MCU, the display circuit is connected with an IO3 (MCU _ IO 3) of the microprocessor MCU and an IO4 (MCU _ IO 4) of the microprocessor, the load resistance switching circuit is respectively connected with the IO2 of the microprocessor MCU, namely the MCU _ IO2, the output end of the circuit to be tested, the second voltage follower is connected with the output end of the circuit to be tested and the second true effective value conversion circuit, and the second true effective value conversion circuit is connected with the AD2 of the microprocessor MCU, namely the MCU _ AD 2.

As shown in fig. 2, the signal source input resistance switching circuit: one end of a second resistor R2 is connected with the MCU _ IO1, the other end of the second resistor R2 is connected with the base of a first triode Q1, the cathode of the first diode D1 is respectively connected with +5V of a power supply and a pin 4 of a first relay K1, the anode of a first diode D1 is connected with one end of a first resistor R1, the other end of the first resistor R1 is simultaneously connected with the collector of the first triode Q1 and a pin 5 of the first relay K1, the emitter of the first triode Q1 is connected with the power ground GND, a pin 1 of the first relay K1 is connected with the INPUT end INPUT of a circuit to be tested, a pin 3 of the first relay K1 is connected with one end of a third resistor R3, and the other end of the third resistor R3 and a pin 2 of the first relay K1 are simultaneously connected with the same-phase end of the first operational amplifier IC1 of the first voltage follower.

As shown in fig. 3, the first voltage follower: the inverting terminal of the first operational amplifier IC1 is connected to the output terminal of the first operational amplifier IC1 and one terminal of the first capacitor C1, respectively, the power supply terminal of the first operational amplifier IC1 is connected to the 12V power supply, the ground terminal of the first operational amplifier IC1 is connected to the ground GND, and the other terminal of the first capacitor C1 is connected to one terminal of the fourth resistor R4 of the amplifier circuit.

As shown in fig. 4, the amplifying circuit: the other end of the fourth resistor R4 is connected to one end of the fifth resistor R5 and the inverting end of the second operational amplifier IC2, the in-phase end of the second operational amplifier IC2 is connected to one end of the sixth resistor R6, the other end of the sixth resistor R6 is connected to the power ground GND, the ground of the second operational amplifier IC2 is connected to the-5V power supply, the power supply of the second operational amplifier IC2 is connected to the +5V power supply, and the output end of the second operational amplifier IC2 and the other end of the fifth resistor R5 are connected to one end of the twelfth resistor R12 and the 3 pins of the second interface J2 of the first true-effective-value conversion circuit.

As shown in fig. 5, the first true significance conversion circuit: the cathode of the fourth diode D4 is connected to the power ground GND, the anode of the fourth diode D4 is connected to one end of the ninth resistor R9, the other end of the ninth resistor R9, one end of the seventh resistor R7 and the cathode of the second diode D2 are simultaneously connected to the + VS power source, the other end of the seventh resistor R7 and the anode of the second capacitor C2 are simultaneously connected to the + VA power source, the cathode of the second capacitor C2 is connected to the power ground GND, the anode of the second diode D2 and the pin 1 of the first interface J1 are simultaneously connected to the +5V power source, the pin 2 of the first interface J1 is connected to the power ground GND, the pin 3 of the first interface J1 and the cathode of the third diode D3 are simultaneously connected to the-5V power source, the anode of the third diode D3, one end of the eighth resistor R8 and one end of the tenth resistor R10 are simultaneously connected to the-VS power source, the other end of the eighth resistor R8 and the cathode of the third capacitor C3 are simultaneously connected to the-VA power source, the anode of the third capacitor C3 is connected to the power ground GND, the other end of the tenth resistor R10 is connected to the cathode of the fifth diode D5, the anode of the fifth diode D5 is connected to the power ground GND, the 6 th pin of the second interface J2 and one end of the seventeenth resistor R17 are connected to the MCU _ AD1, the 4 th pin and the 5 th pin of the second interface J2 are connected to the power ground GND, the 3 th pin of the second interface J2 is connected to one end of the twelfth resistor, the 2 nd pin of the second interface J2 is connected to the power ground GND, the 1 st pin of the second interface J2 is connected to one end of the eighteenth resistor R18, the 3 th pin of the first sliding resistor RW1 is connected to the VA power, the 1 st pin of the first sliding resistor RW1 is connected to the VA power, the 2 nd pin of the first sliding resistor RW1 is connected to one end of the eleventh resistor R11, the 1 st pin of the first true effective value converting chip U1 is connected to one end of the fifteenth resistor R15, one end of the fourth capacitor RW 638 and the fourth capacitor C4 are connected to the fourth capacitor GND, the 4 feet of the first true effective value conversion chip U1 are connected with the other end of an eleventh resistor R11, the 15 feet of the first true effective value conversion chip U1 are connected with one end of a fifth capacitor C5, the other end of the fifth capacitor C5 is simultaneously connected with the other end of a twelfth resistor R12 and one end of a thirteenth resistor R13, the other end of the thirteenth resistor R13 is connected with a power ground GND, the 5 feet of the first true effective value conversion chip U1 are connected with one end of a fourteenth resistor R14, the other end of the fourteenth resistor R14 is connected with a + VA power supply, the 2 feet, 7 feet, 8 feet, 9 feet and 14 feet of the first true effective value conversion chip U1 are suspended, the 6 feet and 11 feet of the first true effective value conversion chip U1 are simultaneously connected with one end of a sixteenth resistor R16, the other end of a seventeenth resistor R17 and one end of an eighth capacitor C8, the 13 feet of the first true effective value conversion chip U1 and one end of the sixth capacitor C6 are simultaneously connected with VA power supply, the other end of the sixth capacitor C6 is connected to the power ground GND, the 16 pin of the first true effective value conversion chip U1 is connected to the other end of the eighteenth resistor R18 and one end of the ninth capacitor C9, the 10 pin of the first true effective value conversion chip U1 is connected to the other end of the eighth capacitor C8, the 12 pin of the first true effective value conversion chip U1 and one end of the seventh capacitor C7 are connected to the VA power supply at the same time, the 3 pin of the first true effective value conversion chip U1 and the other end of the seventh capacitor C7 are connected to the power ground GND at the same time, and the other end of the fifteenth resistor R15 is connected to the other end of the sixteenth resistor R16 and the other end of the ninth capacitor C9 at the same time.

As shown in fig. 6, the auxiliary power supply circuit: the 2-pin of the third interface J3 is connected with a +12V power supply, the 1-pin of the third interface J3 is connected with a power supply ground GND, the 1-pin of the isolation power supply module U2 is connected with a +12V power supply, the 2-pin and the 5-pin of the isolation power supply module U2 are simultaneously connected with the power supply ground GND, the 4-pin of the isolation power supply module U2 is connected with a-5V power supply, and the 6-pin of the isolation power supply module U2 is connected with a +5V power supply.

As shown in fig. 7, the load resistance switching circuit: one end of a twentieth resistor R20 is connected with the MCU _ IO2, the other end of the twentieth resistor R20 is connected with the base electrode of a second triode Q2, the cathode of a sixth diode D6 and the 4 pins of a second relay K2 are simultaneously connected with a +5V power supply, the anode of a sixth diode D6 is connected with one end of a nineteenth resistor R19, the other end of the nineteenth resistor R19 and the 5 pins of a second relay K2 are simultaneously connected with the collector electrode of the second triode Q2, the emitter electrode of the second triode Q2 and one end of a twenty-first resistor R21 are simultaneously connected with a power ground GND, the 1 pin of the second relay K2 and one end of a tenth capacitor C10 of a second voltage follower are simultaneously connected with a circuit OUTPUT terminal OUTPUT, the 3 pin of the second relay K2 is connected with the other end of a twenty-first resistor R21, and the 2 pin of the second relay K2 is suspended.

As shown in fig. 8, the second voltage follower: the in-phase end of the third operational amplifier IC3 is connected to the other end of the tenth capacitor C10, the inverting end and the output end of the third operational amplifier IC3 are connected to the pin 3 of the fifth interface J5 of the second true-value conversion circuit and one end of the twenty-seventh resistor R27, the power supply end of the third operational amplifier IC3 is connected to a +12V power supply, and the ground end of the third operational amplifier IC3 is connected to the power supply ground GND.

As shown in fig. 9, the second true valid value conversion circuit: the cathode of the ninth diode D9 is connected to the power ground GND, the anode of the ninth diode D9 is connected to one end of the twenty-fourth resistor R24, the other end of the twenty-fourth resistor R24, one end of the twenty-second resistor R22 and the cathode of the seventh diode D7 are connected to the + VS power source simultaneously, the other end of the twenty-second resistor R22 and the anode of the eleventh capacitor C11 are connected to the + VA power source simultaneously, the cathode of the eleventh capacitor C11 is connected to the power ground GND, the anode of the seventh diode D7 and the pin 1 of the fourth interface J4 are connected to the +5V power source simultaneously, the pin 2 of the fourth interface J4 is connected to the power ground GND, the pin 3 of the fourth interface J4 and the cathode of the eighth diode D8 are connected to the-5V power source simultaneously, the anode of the eighth diode D8, one end of the twenty-third resistor R23, one end of the twenty-fifth resistor R25 and one end of the twelfth capacitor VA-12 are connected to the-VA power source simultaneously, the anode of the twelfth capacitor C12 is connected to the power ground GND, the other end of the twenty-fifth resistor R25 is connected to the cathode of the twelfth diode D10, the anode of the twelfth diode D10 is connected to the power ground GND, the 6 th pin of the fifth interface J5 and one end of the thirty-second resistor R32 are connected to the MCU _ AD2, the 4 th pin and the 5 th pin of the fifth interface J5 are connected to the power ground GND, the 2 nd pin of the fifth interface J5 is connected to the power ground GND, the 1 st pin of the fifth interface J5 is connected to one end of the thirty-third resistor R33, the 3 rd pin of the second slide rheostat RW2 is connected to the VA power supply, the 1 st pin of the second slide rheostat RW2 is connected to the VA power supply, the 2 nd pin of the second slide rheostat 2 is connected to one end of the twenty-sixth resistor R26, the 1 st pin of the second true-value conversion chip U3 is connected to one end of the thirty-resistor R30 and one end of the thirteenth capacitor C13, the other end of the thirteenth capacitor C4642 is connected to the twenty-sixth resistor R26, a pin 15 of a second true effective value conversion chip U3 is connected with one end of a fourteenth capacitor C14, the other end of a twenty-seventh resistor R27 is connected with the other end of a fourteenth capacitor C14 and one end of a twenty-eighth resistor R28, the other end of a twenty-eighth resistor R28 is connected with a power ground GND, a pin 5 of a second true effective value conversion chip U3 is connected with one end of a twenty-ninth resistor R29, the other end of the twenty-ninth resistor R29 is connected with a VA power supply, a pin 2, a pin 7, a pin 8, a pin 9 and a pin 14 of a second true effective value conversion chip U3 are suspended, a pin 6 and a pin 11 of a second true effective value conversion chip U3 are connected with one end of a thirty-eleventh resistor R31, the other end of a thirty-second resistor R32 and one end of a seventeenth capacitor R17 simultaneously, a pin 13 of a pin of a second true effective value conversion chip U3, one end of a fifteenth capacitor C15 is connected with the VA power supply, and the other end of a fifteenth capacitor C15 is connected with the GND, the 16 pins of the second true effective value conversion chip U3 are connected to the other end of the thirty-third resistor R33 and one end of the eighteenth capacitor C18, the 10 pin of the second true effective value conversion chip U3 is connected to the other end of the seventeenth capacitor C17, the 12 pin of the second true effective value conversion chip U3 and one end of the sixteenth capacitor C16 are connected to the VA power supply, the 3 pin of the second true effective value conversion chip U3 and the other end of the sixteenth capacitor C16 are connected to the ground GND, and the other end of the thirty resistor R30 is connected to the other end of the thirty-first resistor R31 and the other end of the eighteenth capacitor C18.

As shown in fig. 10, the key circuit: one end of a thirty-fourth resistor R34 is connected with a +5V power supply, the other end of the thirty-fourth resistor R34, one end of a first key switch S1 and one end of a nineteenth capacitor C19 are simultaneously connected with an MCU _ RESET, the other end of the first key switch S1 and the other end of the nineteenth capacitor C19 are simultaneously connected with a power supply ground GND, one end of a thirty-fifth resistor R35 is connected with the +5V power supply, the other end of the thirty-fifth resistor R35, one end of a second key switch S2 and one end of a twentieth capacitor C20 are simultaneously connected with the MCU _ IO5, and the other end of the second key switch S2 and the other end of the twentieth capacitor C20 are simultaneously connected with the power supply ground GND.

As shown in fig. 11, the display circuit: a pin 1 of the sixth interface J6 is connected to a pin 1 of the OLED display U4, a pin 2 of the sixth interface J6, one end of a thirty-sixth resistor R36, one end of a thirty-seventh resistor R37, one end of a twenty-first capacitor C21, and a collector of the third transistor Q3 are simultaneously connected to a +5V power supply, a pin 3 of the sixth interface J6 is connected to the other end of the thirty-sixth resistor R36 and a pin 18 of the OLED display U4, a pin 4 of the sixth interface J6 is connected to the other end of the thirty-seventh resistor R37 and a pin 19 of the OLED display U4, a pin 5 of the sixth interface J6 is connected to a pin 14 of the OLED display U4, a pin 6 of the sixth interface J6 is connected to a pin 15 of the OLED display U639, a pin 7 of the sixth interface J6 is connected to a pin 13 of the OLED display U56, a pin 2 of the OLED display U4 is connected to a pin 2 of the fifth capacitor C25, and a pin 863 of the OLED display U867 is connected to a pin 26 and a pin 36867 of the OLED display U863, the 5 pin of the OLED display U4 is connected with the other end of the twenty-six capacitor C26, the 6 pin and the 9 pin of the OLED display U4 are simultaneously connected with the emitter of the third triode Q3, the 7 pin of the OLED display U4 is suspended, the 8 pin, the 10 pin, the 11 pin, the 12 pin, the 16 pin, the 17 pin, the 20 pin, the 21 pin, the 22 pin, the 23 pin, the 24 pin, the 25 pin, the 29 pin and the 30 pin of the OLED display U4 are simultaneously connected with the other end of the twenty-first capacitor C21, the base of the third triode Q3, one end of the thirty-eighth resistor R38, one end of the twenty-second capacitor C22, one end of the twenty-third capacitor C23 and one end of the twenty-fourth capacitor C24, and the pin 26 of the OLED display U4 is connected to the other end of the thirty-eighth resistor R38, the pin 27 of the OLED display U4 is connected to the other end of the twenty-fourth capacitor C24, and the pin 28 of the OLED display U4 is connected to the other end of the twenty-second capacitor C22 and the other end of the twenty-third capacitor C23.

The working process of the utility model is as follows:

the input end of the circuit to be tested is provided with a signal source input resistance switching circuit composed of a relay switch and the like, the relay switch is controlled by the output level of MCU _ IO1 of the microprocessor, one end of the relay switch is additionally connected with a third resistor R3, and the MCU of the microprocessor outputs a 1kHz sine wave signal to the circuit to be tested. When the MCU _ IO1 outputs low level, the first triode Q1 is cut off, the first relay K1 does not act, the sine wave signal is directly connected to the circuit to be tested without passing through the third resistor R3, and the input voltage Vs of the signal source can be measured; on the contrary, when the MCU _ IO1 outputs a high level, the first transistor Q1 is turned on, the relay operates, and the sine wave signal is connected to the circuit to be tested through the third resistor R3, at which time the input voltage Vi of the circuit to be tested can be measured. The calculation formula of the input resistance Ri of the circuit to be tested is as follows:

in the formula I_iA current is input for a signal source.

The output end of the circuit to be tested is connected with the load resistance switching circuit, the load resistance switching circuit is provided with a relay switch, the switching of the relay switch is controlled by the output level of the MCU _ IO2, and one end of the relay switch is additionally connected with a twenty-first resistor R21. When the MCU _ IO2 outputs low level, the second triode Q2 is cut off, the second relay K2 does not act, the output end of the circuit to be tested is suspended, and the no-load output voltage Voc of the circuit to be tested can be measured; on the contrary, when the MCU _ IO2 outputs a high level, the second transistor Q2 is turned on, the second relay circuit K2 operates, and the circuit to be tested is connected to the load resistor R21, at which time the load output voltage Vo of the circuit to be tested can be measured. The calculation formula of the output resistance value Ro of the circuit to be tested is as follows:

according to the measured input voltage Vi and output voltage Vo of the circuit to be measured, the voltage gain Au can be calculated, and the calculation formula is as follows:

the microprocessor MCU samples through the AD converter, stores and operates the obtained numerical value, selects the output quantity through the key, and displays the calculation result on the OLED display screen.

In summary, the utility model adopts the amplifier circuit characteristic testing device, realizes automatic measurement of the characteristic index of the amplifier circuit, has high precision, strong reliability, convenient operation and easy maintenance, and can be popularized and applied in engineering practice testing operation.

Claims

1. An amplifier circuit characteristic testing device, characterized in that: the device comprises a signal source input resistance switching circuit for controlling a signal source input resistance value, a first voltage follower for isolating and eliminating impedance influence between a front-stage circuit and a rear-stage circuit, an amplifying circuit for amplifying a sine wave input signal, a first true effective value conversion circuit for measuring a sine signal true effective value, an auxiliary power circuit for providing a power supply, a load resistance switching circuit for controlling a load resistance value, a second voltage follower for isolating and eliminating impedance influence between the front-stage circuit and the rear-stage circuit, a second true effective value conversion circuit for measuring a sine signal true effective value, a key circuit for realizing resetting and switching a test quantity, a display circuit for displaying a measured value and a microprocessor MCU (microprogrammed control unit);

the signal source input resistance switching circuit is respectively connected with an IO1, a first voltage follower and an input end of a circuit to be tested of the microprocessor MCU, the auxiliary power circuit is respectively connected with a 12V direct current, the signal source input resistance switching circuit, the first voltage follower, an amplifying circuit, a first true effective value conversion circuit, a key circuit, a display circuit, a load resistance switching circuit, a second voltage follower and a second true effective value conversion circuit, the first voltage follower is connected with the amplifying circuit, the amplifying circuit is connected with the first true effective value conversion circuit, the first true effective value conversion circuit is connected with an AD1 of the microprocessor MCU, the key circuit is connected with a RESET of the microprocessor MCU and an IO5 of the microprocessor MCU, the display circuit is connected with the IO3 of the microprocessor MCU and the IO4 of the microprocessor MCU, and the load resistance switching circuit is respectively connected with an IO2 of the MCU microprocessor, The output end of the circuit to be tested is connected, the second voltage follower is respectively connected with the output end of the circuit to be tested and the second true effective value conversion circuit, and the second true effective value conversion circuit is connected with the AD2 of the microprocessor MCU;

the relay switch switching of the signal source input resistance switching circuit is controlled by the IO1 output level of a microprocessor MCU of the microprocessor, the microprocessor MCU outputs a sine wave signal to the circuit to be tested, when the IO1 of the microprocessor MCU outputs a low level, the signal source input voltage can be measured, when the IO1 of the microprocessor MCU outputs a high level, the input voltage of the circuit to be tested can be measured, and therefore the input resistance value of the circuit to be tested is calculated;

the relay switch of the load resistance switching circuit is controlled by the IO2 output level of the microprocessor MCU, when the IO2 of the microprocessor MCU outputs a low level, the no-load output voltage of the circuit to be detected can be measured, otherwise, when the IO2 of the microprocessor MCU outputs a high level, the load output voltage of the circuit to be detected can be measured, the output resistance value of the circuit to be detected is calculated, meanwhile, the voltage gain is calculated, the microprocessor MCU samples through an AD converter, the obtained numerical value is stored and operated, the output quantity is selected through a key, and the calculation result is displayed on an OLED display screen of the display circuit.

2. An amplifier circuit characteristic test apparatus as set forth in claim 1, wherein: the signal source input resistance switching circuit comprises a first resistor, a second resistor, a third resistor, a first diode, a first triode and a first relay;

3. An amplifier circuit characteristic test apparatus as set forth in claim 2, wherein: the first voltage follower comprises a first operational amplifier and a first capacitor;

4. An amplifier circuit characteristic test apparatus as set forth in claim 3, wherein: the amplifying circuit comprises a fourth resistor, a fifth resistor, a sixth resistor and a second operational amplifier;

5. An amplifier circuit characteristic test apparatus as set forth in claim 4, wherein: the first true effective value conversion circuit comprises 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 second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a second diode, a third diode, a fourth diode, a fifth diode, a first slide rheostat, a first interface, a second interface and a first true effective value conversion chip;

6. An amplifier circuit characteristic test apparatus as set forth in claim 5, wherein: the auxiliary power supply circuit comprises a third interface and an isolation power supply module;

7. An amplifier circuit characteristic test apparatus as set forth in claim 6, wherein: the load resistance switching circuit comprises a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a sixth diode, a second triode and a second relay;

8. An amplifier circuit characteristic test apparatus as set forth in claim 7, wherein: the second voltage follower comprises a tenth capacitor and a third operational amplifier;

9. An amplifier circuit characteristic test apparatus as set forth in claim 8, wherein: the second true effective value conversion circuit comprises a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, a twenty-sixth resistor, a twenty-seventh resistor, a twenty-eighth resistor, a twenty-ninth resistor, a thirty-fourth resistor, a thirty-eleventh resistor, a thirty-second resistor, a thirty-third resistor, 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 seventh diode, an eighth diode, a ninth diode, a twelfth polar tube, a second slide rheostat, a fourth interface, a fifth interface and a second true effective value conversion chip;

the cathode of the ninth diode is connected with a power supply ground GND, the anode of the ninth diode is connected with one end of a twenty-fourth resistor, the other end of the twenty-fourth resistor, one end of a twenty-second resistor and the cathode of a seventh diode are simultaneously connected with a + VS power supply, the other end of the twenty-second resistor and the anode of an eleventh capacitor are simultaneously connected with a + VA power supply, the cathode of the eleventh capacitor is connected with the power supply ground GND, the anode of the seventh diode and a pin 1 of a fourth interface are simultaneously connected with a +5V power supply, a pin 2 of the fourth interface is connected with the power supply ground GND, a pin 3 of the fourth interface and a cathode of an eighth diode are connected with a-5V power supply, the anode of the eighth diode, one end of the twenty-third resistor and one end of a twenty-fifth resistor are simultaneously connected with a-VS power supply, and the other end of the twenty-third resistor, The negative electrode of a twelfth capacitor is simultaneously connected with a-VA power supply, the positive electrode of the twelfth capacitor is connected with a power supply ground GND, the other end of the twenty-fifth resistor is connected with the cathode of the twelfth diode, the anode of the twelfth diode is connected with the power supply ground GND, one ends of a 6 pin and a thirty-second resistor of the fifth interface are simultaneously connected with the MCU _ AD2, 4 pins and 5 pins of the fifth interface are simultaneously connected with the power supply ground GND, a 2 pin of the fifth interface is connected with the power supply ground GND, a1 pin of the fifth interface is connected with one end of the thirty-third resistor, a 3 pin of the second slide rheostat is connected with the-VA power supply, a1 pin of the second slide rheostat is connected with the VA power supply, a 2 pin of the second slide rheostat is connected with one end of the twenty-sixth resistor, a1 pin of the second true effective value conversion chip is simultaneously connected with one end of the thirty-resistor, One end of a thirteenth capacitor is connected, the other end of the thirteenth capacitor is connected with a power supply ground GND, 4 pins of a second true effective value conversion chip are connected with the other end of a twenty-sixth resistor, 15 pins of the second true effective value conversion chip are connected with one end of a fourteenth capacitor, the other end of a twenty-seventh resistor is connected with the other end of the fourteenth capacitor and one end of a twenty-eighth resistor, the other end of the twenty-eighth resistor is connected with the power supply ground GND, 5 pins of the second true effective value conversion chip are connected with one end of a twenty-ninth resistor, the other end of the twenty-ninth resistor is connected with a VA power supply, 2 pins, 7 pins, 8 pins, 9 pins and 14 pins of the second true effective value conversion chip are suspended, and 6 pins and 11 pins of the second true effective value conversion chip are connected with one end of a thirty-first resistor and the other end of a thirty-second resistor, One end of a seventeenth capacitor is connected, one end of a 13 pin and one end of a fifteenth capacitor of the second true effective value conversion chip are connected with a + VA power supply, the other end of the fifteenth capacitor is connected with a power supply ground GND, a 16 pin of the second true effective value conversion chip is respectively connected with the other end of a thirty-third resistor and one end of an eighteenth capacitor, a 10 pin of the second true effective value conversion chip is connected with the other end of the seventeenth capacitor, one end of a12 pin and one end of a sixteenth capacitor of the second true effective value conversion chip are connected with the-VA power supply, the other end of a 3 pin and the other end of a sixteenth capacitor of the second true effective value conversion chip are connected with the power supply ground GND, and the other end of the thirty resistor is connected with the other end of a thirty-first resistor and the other end of the eighteenth capacitor.

10. An amplifier circuit characteristic test apparatus as set forth in claim 9, wherein: the key circuit comprises a thirty-fourth resistor, a thirty-fifth resistor, a nineteenth capacitor, a twentieth capacitor, a first key switch and a second key switch;