Common emitter amplifier circuit demonstration board

Abstract

The utility model relates to a common-emitter amplifier circuit demonstration board in the technical field of teaching aid circuit design, which is characterized in that a coupling potentiometer, a coupling change-over switch, a coupling capacitor unit, an RB potentiometer, an RC potentiometer, a bipolar transistor, a filter capacitor, a load unit and a heating unit are integrated on the same circuit substrate, and a plurality of test points are integrated at specific positions of a circuit. Therefore, a user can switch the coupling capacitor at the input end of the control circuit through the coupling change-over switch; the gain is adjusted through the RB potentiometer and the RC potentiometer; a load carried by the circuit is adjusted through the load unit; the temperature of the bipolar transistor is changed through the heating unit; the common-emitter amplifier circuit demonstration device is connected to the oscilloscope through a plurality of test points, so that teachers and students can directly operate and demonstrate various functional characteristics of the common-emitter amplifier circuit, the technical problem that the function and performance characteristics of the common-emitter amplifier circuit are not easy to demonstrate is solved, and the function and performance characteristics of the common-emitter amplifier circuit are efficiently and flexibly demonstrated.

Description

Technical Field

[0001] This utility model belongs to the field of teaching aid circuit design technology, and relates to a common emitter amplifier circuit demonstration board. Background Technology

[0002] As a core application configuration of bipolar transistors, the common-emitter amplifier circuit can effectively amplify weak electrical signals due to its high voltage amplification factor. It is widely used in the field of electronic technology. At the same time, as a basic circuit of analog electronics, it is the core carrier for understanding the transistor amplification principle and the setting of the static operating point.

[0003] However, this circuit presents numerous inconveniences in teaching demonstrations. Traditional teaching relies on discrete component construction, resulting in complex wiring and cumbersome operation due to the need for repeated replacement of bias resistors to adjust the static operating point. Students struggle to visually observe cutoff and saturation distortion caused by operating point offsets, leading to a vague understanding of the core significance of a stable static operating point. Furthermore, the circuit is susceptible to power fluctuations and external interference, resulting in poor repeatability of experimental data and time-consuming troubleshooting. This disconnect between theory and practice hinders students' efficient mastery of key concepts such as voltage amplification calculation and distortion suppression. A more intuitive and convenient teaching demonstration solution is urgently needed to overcome this challenge. Therefore, how to efficiently and flexibly demonstrate the function and performance characteristics of a common-emitter amplifier circuit has become one of the technical problems to be solved. Utility Model Content

[0004] To address the problems existing in the above-mentioned traditional technologies, this utility model proposes a common-emitter amplifier circuit demonstration board, which can efficiently and flexibly demonstrate the functions and performance characteristics of the common-emitter amplifier circuit.

[0005] To achieve the above objectives, the embodiments of this utility model adopt the following technical solutions:

[0006] A common-emitter amplifier circuit demonstration board is provided, including a substrate, test points AIN1, AIN2, AIN3, and AIN4 integrated on the substrate, a coupling potentiometer, a coupling switching switch, a coupling capacitor unit, an RB potentiometer, a first current-limiting resistor, an RC potentiometer, a second current-limiting resistor, a bipolar transistor, a filter capacitor, a load unit, and a heating unit.

[0007] Test points AIN1, AIN2, AIN3, and AIN4 are used to connect to the signal channels of the oscilloscope, respectively. One end of the coupling potentiometer is connected to test point AIN1 and is used to connect to the signal source. The other end of the coupling potentiometer is connected to the base of the bipolar transistor through a coupling switch and a coupling capacitor unit. One end of both the RB potentiometer and the RC potentiometer is used to connect to the power supply. The other end of the RB potentiometer is connected to the base of the bipolar transistor and test point AIN3 through a first current-limiting resistor. The other end of the RC potentiometer is connected to the collector of the bipolar transistor, the positive terminal of the filter capacitor, and test point AIN4 through a second current-limiting resistor. The negative terminal of the filter capacitor is connected to the input terminal of the load unit and test point AIN2. The emitter of the bipolar transistor and the output terminal of the load unit are both grounded.

[0008] The coupling potentiometer is used to switch the capacitance of the coupling capacitor unit; the RB potentiometer and RC potentiometer are used to adjust the electrode connection resistance of the bipolar transistor, respectively; the load unit is used to adjust the load capacity of the bipolar transistor; and the heating unit is used to heat the bipolar transistor.

[0009] In one embodiment, the coupling capacitor unit includes a first coupling capacitor and a second coupling capacitor connected in parallel. The negative terminals of the first coupling capacitor and the second coupling capacitor are respectively used to connect to a coupling switching switch. The positive terminals of the first coupling capacitor and the second coupling capacitor are both connected to the base of a bipolar transistor. The capacitance of the first coupling capacitor is greater than the capacitance of the second coupling capacitor.

[0010] In one embodiment, the load unit includes three parallel and identical load resistor branches, each including a series switching switch and a load resistor.

[0011] In one embodiment, the heating unit includes a ceramic heating element, a heating switch, and a thermometer. The power supply terminal of the ceramic heating element is connected to a power source through the heating switch. The thermometer is in contact with one side of the ceramic heating element and is used to measure the temperature of the ceramic heating element. The other side of the ceramic heating element is in contact with a bipolar transistor and is used to heat the bipolar transistor.

[0012] In one embodiment, the common-emitter amplifier circuit demonstration board described above also includes a power adapter and a power switching switch integrated on the substrate. The power adapter is connected to the input terminal of the power switching switch and the power supply terminal of the heating unit, respectively. The output terminal of the power switching switch is connected to the input terminals of the RB potentiometer and the RC potentiometer, respectively. The power adapter is used to connect to an external power source.

[0013] In one embodiment, the common-emitter amplifier circuit demonstration board described above also includes an oscilloscope adapter integrated on the substrate. The oscilloscope adapter is connected to test points AIN1, AIN2, AIN3 and AIN4 respectively, and is used to connect an oscilloscope.

[0014] In one embodiment, the common-emitter amplifier circuit demonstration board described above also includes a signal source adapter integrated on the substrate. The signal source adapter is connected to one end of a coupling potentiometer and is used to connect to an external signal source.

[0015] In one embodiment, the common-emitter amplifier circuit demonstration board described above also includes a multimeter adapter and an electrode switching switch integrated on the substrate. The multimeter adapter is connected to one end of the electrode switching switch, and the other end of the electrode switching switch is used to connect to the collector or base of the bipolar transistor. The multimeter adapter is used to connect a multimeter.

[0016] In one embodiment, the power adapter, oscilloscope adapter, signal source adapter, and multimeter adapter are all DuPont wire adapters.

[0017] One of the above technical solutions has the following advantages and beneficial effects:

[0018] The aforementioned common-emitter amplifier circuit demonstration board integrates a coupling potentiometer, coupling switch, coupling capacitor unit, RB potentiometer, RC potentiometer, bipolar transistor, filter capacitor, load unit, and heating unit on the same circuit board. It also integrates multiple test points at specific locations within the circuit. This allows users to switch the input coupling capacitor using the coupling switch; adjust the gain using the RB and RC potentiometers; adjust the load using the load unit; change the temperature of the bipolar transistor using the heating unit; and connect to an oscilloscope via multiple test points. This enables teachers and students to directly operate and demonstrate the inverting amplification, voltage gain, load capacity, signal pickup capability, nonlinear distortion, frequency characteristics, and operating point of the common-emitter amplifier circuit. This solves the technical problem of the difficulty in demonstrating the functions and performance characteristics of common-emitter amplifier circuits, thus supporting efficient and flexible demonstrations of their functions and performance characteristics in classroom teaching. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the circuit structure of a common-emitter amplifier circuit demonstration board in one embodiment;

[0021] Figure 2 Here is a waveform diagram for demonstrating the inverted amplification in one embodiment;

[0022] Figure 3 Here is a cutoff distortion waveform diagram from one embodiment;

[0023] Figure 4 Here is a saturation distortion waveform diagram from one embodiment;

[0024] Figure 5 The frequency characteristics are illustrated with corresponding waveforms in one embodiment. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present utility model and are not intended to limit the present utility model. Unless otherwise defined, all technical and scientific terms used in this utility model have the same meaning as commonly understood by one of ordinary skill in the art to which this utility model belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present utility model.

[0026] It should be noted that the reference to "embodiment" in this utility model means that a specific feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of this utility model. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand that the embodiments described in this utility model can be combined with other embodiments. The term "and / or" as used in this utility model specification refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0027] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0028] In one embodiment, such as Figure 1As shown, a common-emitter amplifier circuit demonstration board is provided, including a substrate, test points AIN1, AIN2, AIN3, and AIN4 integrated on the substrate, a coupling potentiometer R1, a coupling switching switch SW1, a coupling capacitor unit, an RB potentiometer R2, a first current-limiting resistor R3, an RC potentiometer R4, a second current-limiting resistor R5, a bipolar transistor Q, a filter capacitor C3, a load unit, and a heating unit. Test points AIN1, AIN2, AIN3, and AIN4 are used to connect to the various signal channels of the oscilloscope. One end of coupling potentiometer R1 is connected to test point AIN1 and used to connect to the signal source. The other end of coupling potentiometer R1 is connected to the base of bipolar transistor Q through coupling switch SW1 and coupling capacitor unit. One end of RB potentiometer R2 and RC potentiometer R4 are both used to connect to the power supply. The other end of RB potentiometer R2 is connected to the base of bipolar transistor Q and test point AIN3 through the first current-limiting resistor R3. The other end of RC potentiometer R4 is connected to the collector of bipolar transistor Q, the positive terminal of filter capacitor C3, and test point AIN4 through the second current-limiting resistor R5. The negative terminal of filter capacitor C3 is connected to the input terminal of the load unit and test point AIN2. The emitter of bipolar transistor Q and the output terminal of the load unit are both grounded. Coupling potentiometer R1 is used to switch the capacitance of the coupling capacitor unit, and RB potentiometer R2 and RC potentiometer R4 are used to adjust the electrode connection resistance of bipolar transistor Q. The load unit is used to adjust the load capacity of the bipolar transistor Q. The heating unit is used to heat the bipolar transistor Q.

[0029] Understandable, such as Figure 1 As shown, the substrate can be a PCB board. The coupling capacitor unit is a circuit composed of at least two coupling capacitors connected in parallel or in series. It is used to adjust the size of the coupling capacitor at the input of the common-emitter amplifier circuit under the selection control of the coupling switch SW1, thereby changing the lower cutoff frequency and the frequency of the input signal of the common-emitter amplifier circuit, to demonstrate the amplitude-frequency and phase-frequency characteristics of the common-emitter circuit. Potentiometer R2 (RB) is used to adjust the base resistance of the bipolar transistor Q, and potentiometer R4 (RC) is used to adjust the collector resistance of the bipolar transistor Q. By adjusting potentiometers R2 and R4, the effect of the RB and RC branch resistances of the bipolar transistor Q on the voltage gain can be demonstrated.

[0030] The load unit is a circuit mainly composed of load elements (such as load resistors). It can switch between multiple load branches to demonstrate the load-driving capability of the common-emitter amplifier circuit. The heating unit is used to heat the bipolar transistor Q, and its circuit structure can be set according to the heating requirements of the bipolar transistor Q. The coupling switch SW1 can be a multi-select switch, which allows direct switching of the corresponding coupling capacitor during the experimental demonstration by toggling the switch position, providing direct convenience for the experimental operation.

[0031] The aforementioned common-emitter amplifier circuit demonstration board integrates a coupling potentiometer R1, a coupling switch SW1, a coupling capacitor unit, an RB potentiometer R2, an RC potentiometer R4, a bipolar transistor Q, a filter capacitor C3, a load unit, and a heating unit on the same circuit board. Multiple test points are integrated at specific locations within the circuit, allowing users to switch the input coupling capacitor using the coupling switch SW1; adjust the gain using the RB potentiometer R2 and the RC potentiometer R4; adjust the load using the load unit; change the temperature of the bipolar transistor Q using the heating unit; and connect to an oscilloscope via multiple test points. This enables teachers and students to directly operate and demonstrate the inverting amplification, voltage gain, load capacity, signal pickup capability, nonlinear distortion, frequency characteristics, and operating point of the common-emitter amplifier circuit. This solves the technical problem of the difficulty in demonstrating the functions and performance characteristics of common-emitter amplifier circuits, thus supporting efficient and flexible demonstrations of their functions and performance characteristics in classroom teaching.

[0032] In one embodiment, such as Figure 1 As shown, the coupling capacitor unit includes a first coupling capacitor C1 and a second coupling capacitor C2 connected in parallel. The negative terminals of the first coupling capacitor C1 and the second coupling capacitor C2 are respectively used to connect to the coupling switching switch SW1, and the positive terminals of the first coupling capacitor C1 and the second coupling capacitor C2 are both connected to the base of the bipolar transistor Q; the capacitance value of the first coupling capacitor C1 is greater than the capacitance value of the second coupling capacitor C2.

[0033] It is understood that in this embodiment, two parallel coupling capacitors are set as coupling capacitor units. By switching the coupling switch SW1 to different positions, different coupling capacitors can be connected to the circuit for experimental demonstration, so as to flexibly demonstrate the amplitude-frequency and phase-frequency characteristics of the common-emitter circuit with the simplest coupling capacitor unit circuit structure.

[0034] In one embodiment, such as Figure 1 As shown, the load unit includes three parallel and identical load resistor branches, each consisting of a series switching switch and a load resistor.

[0035] It is understood that in the above embodiments, one or two load resistor branches can be set, as long as they can be used to change the load-driving capability of the common-emitter amplifier circuit and be demonstrated. In this embodiment, three identical load resistor branches are set, such as... Figure 1 The diagram shows a first load resistor branch consisting of switch SW2 and load resistor R6, a second load resistor branch consisting of switch SW3 and load resistor R7, and a third load resistor branch consisting of switch SW4 and load resistor R8. Each load resistor branch can be connected to its load resistor by pressing a switch in the branch, and disconnected by pressing a switch in the branch. This provides a variety of different load resistor combination adjustment schemes through three different load resistors. While ensuring a simple circuit structure, it achieves a rich variety of common-emitter amplifier circuit load-carrying capacity demonstration effects, thereby further improving the circuit demonstration efficiency.

[0036] In one embodiment, such as Figure 1 As shown, the heating unit includes a ceramic heating element TC, a heating switch SW5, and a thermometer T0. The power supply terminal of the ceramic heating element TC is connected to the power supply through the heating switch SW5. The thermometer T0 is in contact with one side of the ceramic heating element TC and is used to measure the temperature of the ceramic heating element TC. The other side of the ceramic heating element TC is in contact with the bipolar transistor Q and is used to heat the bipolar transistor Q.

[0037] It is understood that this embodiment adopts a transistor heating circuit structure design with a ceramic heating element TC and a heating switch SW5, and is equipped with a thermometer T0 to intuitively display the real-time temperature of the bipolar transistor Q. By connecting the power supply of the ceramic heating element TC through the heating switch SW5 to heat the bipolar transistor Q, the temperature of the bipolar transistor Q can be changed. Furthermore, the collector and base voltages of the bipolar transistor Q can be measured using a multimeter, demonstrating the effect of temperature on the static operating point of the bipolar transistor Q. The circuit structure is simple and easy to operate, further improving the teaching demonstration efficiency of the circuit demonstration board.

[0038] In one embodiment, such as Figure 1 As shown, the common-emitter amplifier circuit demonstration board also includes a power adapter (as indicated by the "Power" label on the substrate) and a power switching switch SW6 integrated on the substrate. The power adapter is connected to the input terminal of the power switching switch SW6 and the power supply terminal of the heating unit, respectively. The output terminal of the power switching switch SW6 is connected to the input terminals of the RB potentiometer R2 and the RC potentiometer R4, respectively. The power adapter is used to connect to an external power supply.

[0039] It is understood that in this embodiment, a power adapter and a power switching switch SW6 can also be directly integrated on the substrate. This allows for direct connection of an external power supply that meets the polarity and voltage requirements to power the bipolar transistor Q and the heating unit through a single power adapter during the teaching demonstration. Furthermore, by switching the power switching switch SW6 to different positions, different voltage levels can be supplied to the bipolar transistor Q, further improving the teaching demonstration efficiency of the circuit demonstration board.

[0040] In one embodiment, such as Figure 1 As shown, the above common-emitter amplifier circuit demonstration board also includes an oscilloscope adapter integrated on the substrate (as indicated by the "oscilloscope" label on the substrate). The oscilloscope adapter connects to test points AIN1, AIN2, AIN3 and AIN4 respectively, and is used to connect an oscilloscope.

[0041] It is understood that in this embodiment, an oscilloscope adapter can also be directly integrated on the substrate, thereby supporting efficient and reliable access to an external oscilloscope to demonstrate the signal waveform of the circuit through a plug-and-play method during the teaching demonstration process, which ultimately further improves the teaching demonstration efficiency of the circuit demonstration board.

[0042] In one embodiment, such as Figure 1 As shown, the common-emitter amplifier circuit demonstration board also includes a signal source adapter integrated on the substrate (as indicated by the "Signal Source" label on the substrate). The signal source adapter is connected to one end of the coupling potentiometer R1 and is used to connect to an external signal source.

[0043] It is understood that, in this embodiment, a signal source adapter can also be directly integrated on the substrate. This allows for convenient plug-and-play access to at least one external signal source (such as the first signal source S1) via a single signal source adapter during teaching demonstrations. By coordinating the coupling potentiometer R1 and coupling capacitor unit to change the frequency characteristics of the input signal, the function and characteristics of the common-emitter amplifier circuit under different input signal characteristics can be efficiently demonstrated, further improving the teaching demonstration efficiency of the circuit demonstration board. Furthermore, the signal source adapter can also be equipped with redundant signal source terminals S2, enabling the demonstration board to be used to extend the input of at least two different external signal sources to the circuit, further expanding the teaching demonstration applications when different signal sources are connected.

[0044] In one embodiment, such as Figure 1As shown, the common-emitter amplifier circuit demonstration board also includes a multimeter adapter (as indicated by the "multimeter" label on the substrate) and an electrode switching switch SW7 integrated on the substrate. The multimeter adapter is connected to one end of the electrode switching switch SW7, and the other end of the electrode switching switch SW7 is used to connect to the collector or base of the bipolar transistor Q. The multimeter adapter is used to connect a multimeter.

[0045] It is understood that in this embodiment, a multimeter adapter and electrode switching switch SW7 can also be directly integrated on the substrate. This allows for efficient and reliable connection of an external multimeter via a single multimeter adapter during teaching demonstrations. Furthermore, the different ranges of the electrode switching switch SW7, such as the two ranges corresponding to the collector or base of the bipolar transistor Q (as indicated by the "collector" and "base" markings on the substrate), enable direct detection of different electrodes of the transistor, thereby further improving the teaching demonstration efficiency of the circuit demonstration board.

[0046] In one embodiment, the aforementioned power adapter, oscilloscope adapter, signal source adapter, and multimeter adapter are all DuPont wire adapters.

[0047] It is understood that, in this embodiment, the entire common-emitter amplifier circuit demonstration board can integrate four DuPont wire adapters on the substrate: a power adapter, an oscilloscope adapter, a signal source adapter, and a multimeter adapter. This allows the demonstration board to be directly connected to a pocket experiment platform, or to be directly connected to discrete external power supplies, oscilloscopes, signal sources, and multimeters. The unified adapter type allows for efficient plugging and unplugging of different external experimental components, thereby further improving the demonstration operation efficiency of the circuit.

[0048] In some implementations, demonstration application examples of the above-described common-emitter amplifier circuit demonstration board are also provided to further demonstrate its effectiveness:

[0049] The common-emitter amplifier circuit demonstration board described above can be equipped with four DuPont wire adapters for connecting the demonstration board to the pocket experimental platform. The input / output configuration (recommended) is as follows: power supply configuration is ±5V to ±12V; input configuration, such as signal S1 with a frequency of 5kHz, peak-to-peak value of 50mVpp, DC current of 0mV, and phase of 0deg; output configuration, such as the oscilloscope's acquisition channels, is channel 1 and channel 2.

[0050] Demonstration instructions:

[0051] Inverting Amplification Demonstration: Observe the input and output waveforms displayed on the oscilloscope, such as... Figure 2 As shown, the inverting amplification of the common-emitter amplifier circuit can be intuitively demonstrated.

[0052] Voltage gain: Adjust the RB potentiometer and the RC potentiometer, and observe the effect of RB and RC on the voltage gain of the common-emitter amplifier circuit. This can verify the theoretically derived amplification factor.

[0053] Output Resistance: Demonstration of the load-driving capability of the common-emitter amplifier circuit. Without distortion, the load-driving capability is visually demonstrated by observing the changes in the output voltage using an oscilloscope after connecting and disconnecting the three load resistors mentioned above.

[0054] Input resistance: Demonstration of the signal pickup capability of the common-emitter amplifier circuit. Without distortion, the signal pickup capability can be visually demonstrated by observing the changes in the output voltage waveform after adjusting the signal source's internal resistance (adjusting the coupling potentiometer R1).

[0055] Nonlinear distortion: The effect of cutoff distortion can be demonstrated by increasing RB or increasing the amplitude of the input signal. The cutoff distortion waveform is as follows: Figure 3 As shown; by decreasing RB, increasing RC, or increasing the input signal amplitude, the effect of saturation distortion can be demonstrated. The saturation distortion waveform is shown below. Figure 4 As shown, CH2 is channel 2 of the oscilloscope, X and Y represent the horizontal axis and vertical axis respectively, X1 and X2 represent two different sampling times on the horizontal axis, and Y1 and Y2 represent two different sampling times on the vertical axis respectively.

[0056] Frequency Characteristics: The amplitude and phase frequency characteristics of the common-emitter circuit can be demonstrated by connecting a Bode timer to an oscilloscope. The lower cutoff frequency of the common-emitter amplifier circuit can be changed by switching the input coupling capacitor using the coupling switch SW1. Alternatively, the amplification factor of the common-emitter amplifier circuit can be visually demonstrated by changing the frequency of the input signal using a Bode timer. Figure 5 As shown.

[0057] Operating point stability demonstration: By turning on the heating unit via the heating switch SW5, the ambient temperature of the bipolar transistor Q can be changed. Furthermore, the collector and base voltages of the bipolar transistor Q can be measured using a multimeter, demonstrating the effect of temperature on the static operating point. For more significant temperature changes, the power supply voltage VCC can be switched to 12V. To prevent power overload, an external power supply can be used to power the experimental box containing the common-emitter amplifier circuit demonstration board.

[0058] The above waveforms Figures 2 to 4 The horizontal axis of the waveform represents time (microseconds), and the vertical axis represents signal amplitude (millivolts). Among the waveforms above, the yellow waveform represents the output of channel 1 of the oscilloscope, and the blue waveform represents the output of channel 2 of the oscilloscope.

[0059] The circuit design of the aforementioned common-emitter amplifier circuit demonstration board fully demonstrates the advantages of a single board for multiple uses and comprehensive coverage. Through reasonable circuit layout and component configuration, this experimental board can complete teaching experiments on various functional characteristics of common-emitter amplifier circuits, including inverting amplification, voltage gain, load-driving capability, signal pickup capability, nonlinear distortion, frequency characteristics, and operating point, comprehensively covering the teaching content of common-emitter amplifier circuits. At the same time, the experimental board is also easy to use. The circuit's operating mode can be easily switched through potentiometers and switches, avoiding errors introduced by frequent circuit disassembly and assembly, and improving the accuracy and reliability of the experiments. This design effectively overcomes the shortcomings of traditional common-emitter amplifier circuit experimental teaching demonstrations, providing great convenience for teaching and experimentation.

[0060] It should be noted that in the specific circuit diagrams of the above 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.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above embodiments only illustrate several implementation methods of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of protection of this utility model. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this utility model, and all of these modifications and improvements fall within the scope of protection of this utility model.

Claims

1. A common-emitter amplifier circuit demonstration board, characterized in that, It includes a substrate, test points AIN1, AIN2, AIN3, and AIN4 integrated on the substrate, a coupling potentiometer, a coupling switching switch, a coupling capacitor unit, an RB potentiometer, a first current-limiting resistor, an RC potentiometer, a second current-limiting resistor, a bipolar transistor, a filter capacitor, a load unit, and a heating unit. Test points AIN1, AIN2, AIN3, and AIN4 are used to connect to the signal channels of the oscilloscope, respectively. One end of the coupling potentiometer is connected to test point AIN1 and is used to connect to the signal source. The other end of the coupling potentiometer is connected to the base of the bipolar transistor through a coupling switch and a coupling capacitor unit. One end of both the RB potentiometer and the RC potentiometer is used to connect to the power supply. The other end of the RB potentiometer is connected to the base of the bipolar transistor and test point AIN3 through a first current-limiting resistor. The other end of the RC potentiometer is connected to the collector of the bipolar transistor, the positive terminal of the filter capacitor, and test point AIN4 through a second current-limiting resistor. The negative terminal of the filter capacitor is connected to the input terminal of the load unit and test point AIN2. The emitter of the bipolar transistor and the output terminal of the load unit are both grounded. The coupling potentiometer is used to switch the capacitance of the coupling capacitor unit; the RB potentiometer and RC potentiometer are used to adjust the electrode connection resistance of the bipolar transistor, respectively; the load unit is used to adjust the load capacity of the bipolar transistor; and the heating unit is used to heat the bipolar transistor.

2. The common-emitter amplifier circuit demonstration board according to claim 1, characterized in that, The coupling capacitor unit includes a first coupling capacitor and a second coupling capacitor connected in parallel. The negative terminals of the first coupling capacitor and the second coupling capacitor are respectively used to connect to the coupling switching switch. The positive terminals of the first coupling capacitor and the second coupling capacitor are both connected to the base of the bipolar transistor. The capacitance value of the first coupling capacitor is greater than the capacitance value of the second coupling capacitor.

3. The common-emitter amplifier circuit demonstration board according to claim 1 or 2, characterized in that, The load unit comprises three parallel and identical load resistor branches, each consisting of a series switching switch and a load resistor.

4. The common-emitter amplifier circuit demonstration board according to claim 3, characterized in that, The heating unit includes a ceramic heating element, a heating switch, and a thermometer. The power supply terminal of the ceramic heating element is connected to a power source through the heating switch. The thermometer is in contact with one side of the ceramic heating element and is used to measure the temperature of the ceramic heating element. The other side of the ceramic heating element is in contact with a bipolar transistor and is used to heat the bipolar transistor.

5. The common-emitter amplifier circuit demonstration board according to claim 3, characterized in that, It also includes a power adapter and a power switching switch integrated on the substrate. The power adapter is connected to the input terminal of the power switching switch and the power supply terminal of the heating unit, respectively. The output terminal of the power switching switch is connected to the input terminals of the RB potentiometer and the RC potentiometer, respectively. The power adapter is used to connect to an external power source.

6. The common-emitter amplifier circuit demonstration board according to claim 3, characterized in that, It also includes an oscilloscope adapter integrated on the substrate, which connects to test points AIN1, AIN2, AIN3 and AIN4 respectively, and is used to connect an oscilloscope.

7. The common-emitter amplifier circuit demonstration board according to claim 3, characterized in that, It also includes a signal source adapter integrated on the substrate, which is connected to one end of the coupling potentiometer and is used to connect to an external signal source.

8. The common-emitter amplifier circuit demonstration board according to claim 3, characterized in that, It also includes a multimeter adapter and an electrode switching switch integrated on the substrate. The multimeter adapter is connected to one end of the electrode switching switch, and the other end of the electrode switching switch is used to connect to the collector or base of the bipolar transistor. The multimeter adapter is used to connect a multimeter.

9. The common-emitter amplifier circuit demonstration board according to any one of claims 5 to 8, characterized in that, The power adapter, oscilloscope adapter, signal source adapter, and multimeter adapter are all DuPont wire adapters.

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