Proportion operation circuit demonstration board based on operational amplifier

Abstract

The utility model relates to a proportion operation circuit demonstration board based on an operational amplifier in the technical field of teaching aid circuit design, which is characterized in that a capacitor, the operational amplifier, a potentiometer and a plurality of change-over switches are integrated on the same circuit substrate, and a plurality of test points are integrated at specific positions of a circuit; an external power supply, a signal source, a universal meter and the like are selectively accessed through a plurality of change-over switches, and connection to an oscilloscope through a plurality of test points is supported. Therefore, teachers and students can directly operate and demonstrate the functional characteristics of circuits such as an anti-phase proportional operation circuit, an in-phase proportional operation circuit, a voltage follower and a single-power-supply anti-phase proportional operation circuit, and the technical problem that the functional and performance characteristics of the proportional operation circuit are not easy to demonstrate is solved. The function and performance characteristics of the proportion operation circuit based on the operational amplifier can be efficiently and flexibly demonstrated.

Description

TECHNICAL FIELD

[0001] The utility model belongs to teaching aid circuit design technical field relates to a kind of proportional operation circuit demonstration board based on operational amplifier. BACKGROUND

[0002] Proportional operation circuit based on operational amplifier (including inverting, same-phase proportional amplification circuit) is the core basic circuit of analog electronic technology, with the advantages of simple structure, precise controllable amplification multiple, good linearity, widely used in electronic system.It can realize the quantitative amplification of input signal by adjusting the ratio of feedback resistance and input resistance, commonly used for sensor weak signal conditioning, signal preprocessing of data acquisition system, signal amplification in industrial measurement and control, and signal amplification module of oscilloscope, multimeter and other measuring instruments, is the key link connecting analog signal source and subsequent processing circuit.

[0003] However, in the teaching demonstration process, the circuit has obvious inconvenience.Traditional teaching is mostly built with discrete components, with complicated wiring and repeated resistance replacement for parameter adjustment, and the amplification multiple cannot be adjusted in real time.Students cannot intuitively observe the quantitative relationship between resistance parameter and output signal, and the understanding of circuit core characteristics is only at the theoretical level.Meanwhile, the circuit is easily disturbed by external interference, with large experimental data fluctuation and difficult fault troubleshooting, resulting in low teaching demonstration efficiency and poor intuitiveness, which makes it difficult to effectively link theory and practice, and there is an urgent need for convenient and efficient demonstration scheme to optimize teaching effect. UTILITY MODEL CONTENT

[0004] In view of the problems existing in the above-mentioned traditional technology, the utility model provides a proportional operation circuit demonstration board based on operational amplifier, which can efficiently and flexibly demonstrate the function and performance characteristics of proportional operation circuit based on operational amplifier.

[0005] To achieve the above purpose, the utility model embodiment adopts the following technical solutions:

[0006] A proportional operation circuit demonstration board based on operational amplifier is provided, comprising a substrate, an integrated capacitor C on the substrate, test points AIN1, AIN2 and AIN3, an operational amplifier, a potentiometer, switching switches SW1, SW2, SW3, SW4 and SW5.

[0007] One end of the capacitor C is connected to the switching switch SW1, the other end of the capacitor C is used to connect the first signal source, the switching switch SW1 is connected to the inverting input end of the operational amplifier through the test point AIN2, the test point AIN1 and the switching switch SW2 are both connected to the non-inverting input end of the operational amplifier, the switching switch SW3 is connected to the two input ends of the operational amplifier respectively, the switching switch SW4 is connected across the output end and the inverting input end of the operational amplifier, the switching switch SW5 is connected to the negative power supply end of the operational amplifier, and the potentiometer is connected in series between the output end and the feedback resistor of the operational amplifier;

[0008] The test point AIN1, the test point AIN2 and the test point AIN3 are used to connect the signal channels of the oscilloscope respectively, the switching switch SW1 is used to select to access the first signal source, the ground or the capacitor C, the switching switch SW2 is used to select to access the first signal source, the 1 / 2 power supply or the ground, the switching switch SW3 is used to select to connect the non-inverting input end or the inverting input end of the operational amplifier to the multimeter, the switching switch SW4 is used to switch the feedback resistor branch of the operational amplifier to be connected or disconnected, the switching switch SW5 is used to switch the negative power supply end of the operational amplifier to be connected to the negative power supply or the ground, and the potentiometer is used to adjust the size of the negative feedback resistor of the operational amplifier.

[0009] In one of the embodiments, the operational amplifier-based proportional operation circuit demonstration board further comprises a power adapter interface integrated on the substrate, the power adapter interface is connected to the positive power supply end of the operational amplifier, the switching switch SW5 and the switching switch SW2 respectively, and the power adapter interface is used to connect an external power supply.

[0010] In one of the embodiments, the operational amplifier-based proportional operation circuit demonstration board further comprises an oscilloscope adapter interface integrated on the substrate, the oscilloscope adapter interface is connected to the test point AIN1, the test point AIN2 and the test point AIN3 respectively, and the oscilloscope adapter interface is used to connect an oscilloscope.

[0011] In one of the embodiments, the operational amplifier-based proportional operation circuit demonstration board further comprises a signal source adapter interface integrated on the substrate, the signal source adapter interface is connected to the switching switch SW1 and the switching switch SW2 respectively, and the signal source adapter interface is used to connect an external first signal source.

[0012] In one of the embodiments, the operational amplifier-based proportional operation circuit demonstration board further comprises a multimeter adapter interface integrated on the substrate, the multimeter adapter interface is connected to the switching switch SW3, and the multimeter adapter interface is used to connect a multimeter.

[0013] In one of the embodiments, the power adapter interface, the oscilloscope adapter interface, the signal source adapter interface and the multimeter adapter interface are all DuPont wire adapter interfaces.

[0014] One of the technical solutions has the following advantages and beneficial effects:

[0015] The above-mentioned proportional operation circuit demonstration board based on an operational amplifier integrates a capacitor, an operational amplifier, a potentiometer and a plurality of switching switches on the same circuit substrate, integrates a plurality of test points at specific positions of the circuit, selects access to external power supply, signal source and multimeter through the plurality of switching switches, and supports connection to an oscilloscope through the plurality of test points, so that teachers and students can directly operate the functions and characteristics of the phase inversion proportional operation circuit, the in-phase proportional operation circuit, the voltage follower and the single power supply phase inversion proportional operation circuit, and the technical problem that the functions and performance characteristics of the proportional operation circuit are not easy to demonstrate is solved, and the functions and performance characteristics of the proportional operation circuit based on the operational amplifier can be efficiently and flexibly demonstrated. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 FIG. 1 is a circuit structure schematic diagram of a proportional operation circuit demonstration board based on an operational amplifier in an embodiment;

[0018] Figure 2 FIG. 4 is a waveform diagram displayed by an oscilloscope when demonstrating the in-phase amplification of the in-phase proportional operation circuit in an embodiment;

[0019] Figure 3 FIG. 4 is a waveform diagram displayed by an oscilloscope when demonstrating the in-phase amplification of the in-phase proportional operation circuit in an embodiment;

[0020] Figure 4 FIG. 7 is a waveform diagram displayed by an oscilloscope when demonstrating the voltage following function of the voltage follower in an embodiment;

[0021] Figure 5 FIG. 8 is a distorted waveform diagram of the top output signal displayed by an oscilloscope when demonstrating the voltage following function of the voltage follower in an embodiment;

[0022] Figure 6 FIG. 8 is a distorted waveform diagram of the top output signal displayed by an oscilloscope when demonstrating the voltage following function of the voltage follower in an embodiment;

[0023] Figure 7 FIG. 9 is a waveform diagram displayed by an oscilloscope when demonstrating the input-output relationship of the single power supply phase inversion proportional operation circuit in an embodiment.

[0024] Reference signs: first redundant power supply port +V, second redundant power supply port -V, first power supply port +5V, second power supply port -5V, ground terminal GND, capacitor C, test point AIN1, test point AIN2, test point AIN3, operational amplifier AP, resistor R1, resistor R2, feedback resistor R3, potentiometer R4, switching switch SW1, switching switch SW2, switching switch SW3, switching switch SW4, switching switch SW5, first signal source connection port S1, power supply VCC, second signal source connection port S2, first current measurement terminal A, second current measurement terminal mA, common mode voltage measurement terminal COM, voltage measurement terminal V. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following will combine with the drawings and examples, make further detailed description to the utility model. It should be understood that the specific examples described here are only used to explain the utility model, and are not used to limit the utility model. Unless otherwise defined, all technical and scientific terms used in the utility model are the same as the meanings commonly understood by the person skilled in the art belonging to the technical field of the utility model. The terms used in the specification of the utility model are only for the purpose of describing the specific examples, and are not intended to limit the utility model.

[0026] It should be noted that the reference to "examples" in the utility model means that the specific features, structures or characteristics described in conjunction with the examples can be included in at least one example of the utility model. The phrase is shown at various places in the specification does not necessarily refer to the same example, nor is it an independent or alternative example that is not mutually exclusive with other examples. Those skilled in the art can understand that the examples described in the utility model can be combined with other examples. The term "and / or" used in the specification of the utility model means one or more of the associated listed items and all possible combinations, and includes these combinations.

[0027] The embodiments of the utility model will be described in detail below in conjunction with the drawings in the examples of the utility model.

[0028] In one example, as Figure 1As shown, a demonstration board for a proportional operational amplifier circuit based on an operational amplifier is provided, including a substrate, a capacitor C integrated on the substrate, test points AIN1, AIN2, and AIN3, an operational amplifier AP, a potentiometer R4, and switches SW1, SW2, SW3, SW4, and SW5. One end of capacitor C is connected to switch SW1, and the other end of capacitor C is used to connect to a first signal source. Switch SW1 is connected to the inverting input terminal of operational amplifier AP through test point AIN2. Test point AIN1 and switch SW2 are both connected to the non-inverting input terminal of operational amplifier AP. Switch SW3 is connected to both input terminals of operational amplifier AP. Switch SW4 is connected across the output terminal and the inverting input terminal of operational amplifier AP. Switch SW5 is connected to the negative power supply terminal of operational amplifier AP. Potentiometer R4 is connected in series between the output terminal of operational amplifier AP and feedback resistor R3. Test points AIN1, AIN2, and AIN3 are used to connect to the various signal channels of the oscilloscope. Switch SW1 is used to select whether to connect to the first signal source, ground, or connect capacitor C. Switch SW2 is used to select whether to connect to the first signal source, 1 / 2 power supply, or ground. Switch SW3 is used to select whether to connect the non-inverting or inverting input of the operational amplifier AP to the multimeter. Switch SW4 is used to switch the feedback resistor branch of the operational amplifier AP to be connected or disconnected. Switch SW5 is used to switch the negative power supply terminal of the operational amplifier AP to be connected to the negative power supply or ground. Potentiometer R4 is used to adjust the value of the negative feedback resistor of the operational amplifier AP.

[0029] Understandable, such as Figure 1 As shown, the substrate can be a PCB board, and capacitor C is a coupling capacitor that allows the first signal source when this branch is selected to be connected to the inverting input of the operational amplifier AP through the coupling capacitor, in order to demonstrate the input and output waveforms of the inverting proportional operational circuit. The operational amplifier AP itself can also include basic components such as resistors R1, R2, and feedback resistor R3. Switches SW1, SW2, SW3, SW4, and SW5 can all be multi-select switches, which can be used to directly switch the corresponding signal, branch, and power supply during the experimental demonstration by toggling the switch position, providing direct convenience for the experimental operation. The negative feedback resistor of the operational amplifier AP can be directly adjusted by adjusting potentiometer R4 to achieve changes in the voltage amplification factor during the circuit demonstration.

[0030] Specifically, the above-mentioned operational amplifier-based proportional operation circuit demonstration board can demonstrate the functional characteristics of various circuit types, such as inverting proportional operation circuit, non-inverting proportional operation circuit, voltage follower, and single-supply inverting proportional operation circuit, through the combination of the above-mentioned components. For specific demonstration examples, please refer to the examples below.

[0031] The above-mentioned operational amplifier-based proportional operation circuit demonstration board integrates the capacitor C, the operational amplifier AP, the potentiometer R4 and a plurality of switching switches on the same circuit substrate, integrates a plurality of test points at specific positions of the circuit, selects access to external power supply, signal source and multimeter through the plurality of switching switches, and supports connection to the oscilloscope through the plurality of test points, so that teachers and students can directly operate the functions and characteristics of the phase inversion proportional operation circuit, the in-phase proportional operation circuit, the voltage follower and the single power supply phase inversion (or in-phase) proportional operation circuit, etc. The technical problem that the functions and performance characteristics of the proportional operation circuit are not easy to demonstrate is solved, and the functions and performance characteristics of the operational amplifier-based proportional operation circuit can be efficiently and flexibly demonstrated.

[0032] In one embodiment, as shown in Figure 1 The above-mentioned operational amplifier-based proportional operation circuit demonstration board further includes a power supply adapter integrated on the substrate (as shown by the "power supply" mark on the substrate), which is connected to the positive power supply end of the operational amplifier AP, the switching switch SW5 and the switching switch SW2. The power supply adapter is used to connect the external power supply.

[0033] It can be understood that in this embodiment, the power supply adapter can also be integrated directly on the substrate. The power supply adapter can be provided with a first redundant power port +V, a second redundant power port -V, a first power supply port +5V, a second power supply port -5V and a ground terminal GND. Thus, during the teaching demonstration process, the operational amplifier AP can be powered by directly connecting different polarity external power supplies through one power supply adapter, and when the switching switch SW5 is switched to different gears, the negative power supply end of the operational amplifier AP is switched to access the negative power supply or the ground. When the switching switch SW2 is switched to different gears, the in-phase input end of the operational amplifier AP accesses the power supply gear VCC / 2 as a reference power supply. Finally, the teaching demonstration operation efficiency of the circuit demonstration board is improved.

[0034] In one embodiment, as shown in Figure 1 The above-mentioned operational amplifier-based proportional operation circuit demonstration board further includes an oscilloscope adapter integrated on the substrate (as shown by the "oscilloscope" mark on the substrate), which is connected to the test point AIN1, the test point AIN2 and the test point AIN3. The oscilloscope adapter is used to connect the oscilloscope.

[0035] It can be understood that in this embodiment, the oscilloscope adapter can also be integrated directly on the substrate. Thus, during the teaching demonstration process, the circuit can be efficiently and reliably demonstrated by plugging in an external oscilloscope through one oscilloscope adapter. Finally, the teaching demonstration operation efficiency of the circuit demonstration board is improved.

[0036] In one embodiment, as shown in Figure 1 The above-mentioned operational amplifier-based proportional operation circuit demonstration board further includes a signal source adapter integrated on the substrate (as shown by the "signal source" mark on the substrate), which is connected to the switching switch SW1 and the switching switch SW2, respectively, and is used to connect an external first signal source.

[0037] It can be understood that in this embodiment, the signal source adapter can also be integrated directly on the substrate, so that at least one external signal source (such as the first signal source) can be conveniently accessed in a plug-in manner through a signal source adapter (such as the first signal source connection port S1) during teaching demonstration, and the different input terminals of the operational amplifier AP can be selected to access the corresponding signal source by switching the switching switch SW1 and the switching switch SW2 to different gears as needed, thereby efficiently realizing the selection of different input terminals of the operational amplifier AP to access the corresponding signal source, and further improving the teaching demonstration operation efficiency of the circuit demonstration board. In addition, the signal source adapter can also be provided with a redundant second signal source connection port S2, which can be used to expand the access of two different external signal sources for signal input to the circuit, thereby facilitating the demonstration of the circuit phenomenon when different signal sources are accessed.

[0038] In one embodiment, as shown in Figure 1 The above-mentioned operational amplifier-based proportional operation circuit demonstration board further includes a multimeter adapter integrated on the substrate (as shown by the "multimeter" mark on the substrate), which is connected to the switching switch SW3 and is used to connect a multimeter. The multimeter adapter is provided with commonly used first current measurement terminals A, second current measurement terminals mA, common-mode voltage measurement terminals COM, voltage measurement terminals V, etc., which can be used to measure the current and voltage parameters of the input terminals of the operational amplifier AP, respectively.

[0039] It can be understood that in this embodiment, the multimeter adapter can also be integrated directly on the substrate, so that an external multimeter can be efficiently and reliably accessed in a plug-in manner through a multimeter adapter during teaching demonstration, and the different gears of the switching switch SW3, such as two gears, are respectively corresponding to the inverting input terminal and the non-inverting input terminal of the operational amplifier AP, thereby realizing the direct detection of different input terminals of the circuit and improving the teaching demonstration operation efficiency of the circuit demonstration board.

[0040] In one embodiment, the power adapter, the oscilloscope adapter, the signal source adapter, and the multimeter adapter are all DuPont line adapters.

[0041] It can be understood that in the embodiment, the entire differential amplifier circuit demonstration board can be connected with the pocket experiment platform directly or connected with the separate external power supply, oscilloscope, signal source and multimeter directly through the integration of four DuPont line adapters: power adapter, oscilloscope adapter, signal source adapter and multimeter adapter on the substrate. The unified adapter type can reduce the difficulty of adaptation of different external platforms, thereby improving the demonstration operation efficiency of the circuit.

[0042] In some embodiments, some demonstration application examples of the above-mentioned operational amplifier-based proportional operation circuit demonstration board are also provided to further demonstrate the effect thereof:

[0043] The above-mentioned operational amplifier-based proportional operation circuit demonstration board is matched with four DuPont line adapters for connecting the demonstration circuit board with the pocket experiment platform. The circuit types that can be demonstrated include: inverting proportional operation circuit, non-inverting proportional operation circuit, voltage follower and single power supply powered inverting proportional operation circuit.

[0044] Input and output configuration (recommended), input configuration: input signal frequency <10 kHz, peak-to-peak value <7V (when testing the voltage follower) or peak-to-peak value <500mV (when testing the proportional operation circuit). The output configuration is to enable the oscilloscope channels 1 to 3, which are respectively connected with the test points AIN1 to AIN3 of the oscilloscope adapter.

[0045] Demonstration of inverting proportional operation circuit: the input signal is set to a frequency of 5 kHz and a peak-to-peak value of 200mV. The switch is set to: the inverting terminal is switched to the first signal source connection port S1 through the switching switch SW1, the non-inverting terminal is switched to the ground terminal GND through the switching switch SW2, the negative power supply is switched to the second power supply port -5V through the switching switch SW5, and the switching switch SW4 is switched to be disconnected. The input and output waveforms are observed as shown in Figure 2 The inverting amplification of the inverting proportional operation circuit is demonstrated. The voltage amplification factor can be obtained by calculating the ratio of the peak-to-peak values of channel 3 and channel 2. Adjust the potentiometer R4 to observe the effect of the negative feedback resistor on the voltage amplification factor. It should be noted that clockwise rotation of the potentiometer R4 reduces the negative feedback resistor and the voltage amplification factor, and the output voltage decreases; counterclockwise rotation of the potentiometer R4 is the opposite. The abscissa of the oscilloscope display waveform is time (microsecond), and the ordinate is signal amplitude (millivolt). The coordinate axes of the waveforms in the following Figures 3 to 7

[0046] ​Demonstration of the in-phase proportional operation circuit: the input signal is set to a frequency of 5 kHz and a peak-to-peak value of 200 mV. The switch is set to the in-phase terminal, which is switched to the first signal source terminal port S1 by the switching switch SW2, the anti-phase terminal, which is switched to the ground terminal GND by the switching switch SW1, the negative power supply, which is switched to the second power supply terminal -5 V by the switching switch SW5, and the switching switch SW4 is switched to the off position.

[0047] As shown in the input and output waveforms Figure 3 , the in-phase amplification function of the in-phase proportional operation circuit is demonstrated. The voltage amplification factor can be obtained by calculating the ratio of the peak-to-peak values of channel 3 and channel 1. Adjust the potentiometer R4 to observe the effect of the negative feedback resistance on the voltage amplification factor. Note that clockwise rotation of the potentiometer R4 reduces the negative feedback resistance and the voltage amplification factor, resulting in a decrease in output voltage. Conversely, counterclockwise rotation of the potentiometer R4 has the opposite effect.

[0048] Demonstration of the voltage follower: the input signal is set to a frequency of 5 kHz and a peak-to-peak value of 2000 mV. The switch is set to the in-phase terminal, which is switched to the first signal source terminal port S1 by the switching switch SW2, the anti-phase terminal, which is switched to the ground terminal GND by the switching switch SW1, the negative power supply, which is switched to the second power supply terminal -5 V by the switching switch SW5, and the switching switch SW4 is switched to the on position.

[0049] As shown in the input and output waveforms Figure 4 , the voltage following function of the voltage follower is demonstrated. The voltage amplification factor can be obtained by calculating the ratio of the peak-to-peak values of channel 3 and channel 1. Increase the input signal peak-to-peak value and observe the output signal distortion. When the input signal peak-to-peak value exceeds a certain value (7400 mV in the figure), the output signal begins to appear distorted at the top, as shown in Figure 5 . When the input signal continues to increase (more than 8800 mV in the figure), the output signal begins to appear distorted at the bottom, as shown in Figure 6 . The maximum undistorted output amplitude of the operational amplifier can be calculated.

[0050] Demonstration of the single power supply powered anti-phase proportional operation circuit: the input signal is set to a frequency of 5 kHz and a peak-to-peak value of 200 mV. The switch is set to the anti-phase terminal, which is switched to the capacitor C by the switching switch SW1, so that the first signal source is input through the first signal source terminal port S1 and the capacitor C, the in-phase terminal is switched to the power supply gear VCC / 2 by the switching switch SW2, the negative power supply is switched to the ground terminal GND by the switching switch SW5, the switching switch SW4 is switched to the off position, the power supply VCC is 5 volts and can be connected through the first power supply terminal +5 V, and correspondingly, the 1 / 2 power supply, i.e. the power supply gear VCC / 2, corresponds to the input power supply which is half of the voltage of the power supply VCC, which can be realized by connecting the power supply VCC through the commonly used voltage dividing resistor.

[0051] As shown in the input and output waveformsFigure 7 The input-output relationship of the single power supply inverting proportional operation circuit is demonstrated. It can be observed that the DC is superimposed in the output AC signal. Adjust the potentiometer R4, and observe the influence of the negative feedback resistor on the voltage amplification factor. It should be noted that, when rotating the potentiometer R4 clockwise, the negative feedback resistor becomes smaller, the voltage amplification factor decreases, and the output voltage decreases; when rotating the potentiometer R4 counterclockwise, the opposite is true.

[0052] The above waveforms Figures 2 to 7 Among them, the yellow waveform is the output of channel 1 of the oscilloscope, the blue waveform is the output of channel 2 of the oscilloscope, and the purple waveform is the output of channel 3 of the oscilloscope.

[0053] The circuit design of the above-mentioned operational amplifier-based proportional operation circuit demonstration board fully demonstrates the advantages of one board, multiple uses, and one board full coverage. Through reasonable circuit layout and component configuration, the operational amplifier-based proportional operation circuit demonstration board can complete experimental teaching demonstration of inverting proportional operation circuit, non-inverting proportional operation circuit, voltage follower, and single power supply inverting proportional operation circuit, and fully covers the teaching content of the operational amplifier-based proportional operation circuit. At the same time, the use of the proportional operation circuit demonstration board is relatively simple. By switching the switch and setting the potentiometer, the working mode of the circuit can be easily switched, avoiding errors caused by frequent disassembly and assembly of the circuit, and improving the accuracy and reliability of the experiment. This design fully overcomes the shortcomings of traditional proportional operation circuit experiments, and provides great convenience for teaching and experiments.

[0054] It should be noted that in the specific circuit diagrams of the above-mentioned circuit parts, if the pins in different circuit diagrams are marked with the same label, it means that the pins with the same label are connected.

[0055] The technical features of the above embodiments can be combined in any way. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0056] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the protection scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application.

Claims

1. An op-amp-based proportional operation circuit demonstration board, characterized by comprising: The circuit comprises a substrate, a capacitor C integrated on the substrate, a test point AIN1, a test point AIN2, a test point AIN3, an operational amplifier, a potentiometer, a switching switch SW1, a switching switch SW2, a switching switch SW3, a switching switch SW4 and a switching switch SW5. One end of the capacitor C is connected to the switching switch SW1, the other end of the capacitor C is used to connect a first signal source, the switching switch SW1 is connected to the inverting input end of the operational amplifier through the test point AIN2, the test point AIN1 and the switching switch SW2 are both connected to the non-inverting input end of the operational amplifier, the switching switch SW3 is connected to the two input ends of the operational amplifier respectively, the switching switch SW4 is connected between the output end and the inverting input end of the operational amplifier, and the switching switch SW5 is connected to the negative power supply end of the operational amplifier. The test point AIN1, the test point AIN2 and the test point AIN3 are respectively used to connect each signal channel of an oscilloscope, the switching switch SW1 is used to select to access the first signal source, ground or connect the capacitor C, the switching switch SW2 is used to select to access the first signal source, 1 / 2 power supply or ground, the switching switch SW3 is used to select to connect the non-inverting input end or the inverting input end of the operational amplifier to a multimeter, the switching switch SW4 is used to switch the feedback resistor branch of the operational amplifier to be connected or disconnected, the switching switch SW5 is used to switch the negative power supply end of the operational amplifier to be connected to a negative power supply or ground, and the potentiometer is used to adjust the size of the negative feedback resistor of the operational amplifier.

2. The op-amp-based proportional operation circuit demonstration board according to claim 1, characterized by, The circuit further comprises a power adapter integrated on the substrate, the power adapter is connected to the positive power supply end of the operational amplifier, the switching switch SW5 and the switching switch SW2 respectively, and the power adapter is used to connect an external power supply.

3. The op-amp-based proportional operation circuit demonstration board according to claim 1 or 2, characterized by The circuit further comprises an oscilloscope adapter integrated on the substrate, the oscilloscope adapter is connected to the test point AIN1, the test point AIN2 and the test point AIN3 respectively, and the oscilloscope adapter is used to connect the oscilloscope.

4. The op-amp-based proportional operation circuit demonstration board according to claim 3, characterized by The circuit further comprises a signal source adapter integrated on the substrate, the signal source adapter is connected to the switching switch SW1 and the switching switch SW2 respectively, and the signal source adapter is used to connect an external first signal source.

5. The op-amp-based proportional operation circuit demonstration board according to claim 3, characterized by The circuit further comprises a multimeter adapter integrated on the substrate, the multimeter adapter is connected to the switching switch SW3, and the multimeter adapter is used to connect a multimeter.

6. The op-amp-based proportional operation circuit demonstration board according to claim 3, characterized by The power adapter, the oscilloscope adapter, the signal source adapter and the multimeter adapter are all DuPont wire adapters.

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