A test circuit, test method and test system for a transconductance curve

Abstract

The application provides a test circuit, a test method and a test system of a transconductance curve. On a device of a constant current source, an external modulation module is arranged. The modulation module comprises a voltage control unit and a following sub-circuit. The voltage control unit is used for outputting an adjustable voltage to the following sub-circuit. The following sub-circuit is connected to a gate of a measured device. The following sub-circuit is used for generating a modulation voltage according to the adjustable voltage and a constant current source voltage. The on-off rate of the measured device is modulated by the modulation voltage, so as to control the voltage between a first pole and a second pole of the measured device. The voltage between the first pole and the second pole is equal to the adjustable voltage. The high-end output voltage output by the constant current source is used to realize the constant voltage state between the first pole and the second pole of the measured device, and the test of the transconductance curve is realized. The cost of the whole test system is reduced. Meanwhile, the module circuit is small in size and flexible in operation.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device testing technology, and in particular to a test circuit, test method and test system for transconductance curves. Background Technology

[0002] Power devices require static parameter testing before leaving the factory to verify that their parameters are within specified ranges and meet factory requirements. The output characteristic curve and transmission characteristic curve of a power device are collectively referred to as transconductance. Gfs Curve testing. Current testing methods for transconductance include... Figure 1 The diagram shows an IGBT (Insulated Gate Bipolar Transistor) power device as an example. Figure 1 middle, GE The terminal uses a constant pulse voltage source, for GE The terminal provides a voltage with variable pulse width and adjustable amplitude. CE The terminal uses a feedback module to provide current to the measured device.

[0003] Transconductance curve is mainly measured CE Terminals at different voltages and currents flowing through power devices I c The relationships between the curves are as follows: I c = f ( V CE ), in different GE In such cases, multidimensional curves can be plotted, such as... Figure 2 and Figure 3 As shown, Figure 2 For different V ce =20V, different I c Current corresponding V ge Transmission characteristic curve, Figure 3 For different V ge =20V, different I c Current corresponding V ge Output characteristic curve. For Figure 2 and Figure 3 It is not possible to use a constant current source for testing; a constant current source is required. CE The voltage between them was tested.

[0004] Testing the saturation forward voltage V cesat Body diode forward voltage dropVF When testing power device parameters, a constant current source is needed. The items tested by a complete test system include power device saturation on-voltage V cesat , body diode on-voltage drop VF , transconductance, so a complete test system needs a feedback module and a constant current source. Simultaneous use of a constant current source and a feedback module in a test system to test the above parameters increases the cost of system equipment, the volume is large, and the control of two devices for testing a device is complex. SUMMARY

[0005] Therefore, it is necessary to provide a power device transconductance curve test circuit, test method and test system to solve the problem that the simultaneous use of a constant current source subcircuit and a feedback module in a transconductance test system increases the cost of system equipment, the volume is large, and the control of two devices for testing a device is complex.

[0006] To solve the above technical problems, in a first aspect, an embodiment of the present application provides a transconductance curve test circuit, which comprises a constant current source subcircuit, a modulation module and a test module.

[0007] One end of the constant current source subcircuit is connected to a first pole of a device under test, the other end of the constant current source subcircuit is connected to a second pole of the device under test, and the constant current source subcircuit inputs a constant current source path current and a constant current source voltage to the device under test; wherein the first pole is a drain and the second pole is a source, or the first pole is a collector and the second pole is an emitter.

[0008] The modulation module comprises a voltage control unit and a follower subcircuit, the voltage control unit is used to output an adjustable voltage to the follower subcircuit, the follower subcircuit is connected to a gate of the device under test, and the follower subcircuit is used to generate a modulation voltage according to the adjustable voltage and the constant current source voltage, modulate the on-rate of the device under test by the modulation voltage, control the voltage between the first pole and the second pole of the device under test, and make the voltage between the first pole and the second pole equal to the adjustable voltage.

[0009] The test module is used to detect the voltage between the gate and the second pole of the device under test, and generate a transconductance curve according to the constant current source path current and the voltage between the gate and the second pole of the device under test.

[0010] In some possible implementation manners, the device under test comprises an insulated gate bipolar transistor (IGBT) power device, a metal oxide semiconductor field effect transistor (MOSFET) and a bipolar transistor.

[0011] In some possible implementation manners, the constant current source subcircuit inputs the constant current source voltage Vc 1 to the first pole of the device under test.

[0012] an input terminal of the follower sub-circuit is connected to the first electrode of the device under test and the voltage control unit, and an output terminal of the follower sub-circuit is connected to the gate of the device under test;

[0013] the follower sub-circuit comprises a first operational amplifier, a non-inverting input terminal of the first operational amplifier is connected to the first electrode of the device under test, and an inverting input terminal of the first operational amplifier is connected to the voltage control unit;

[0014] the follower sub-circuit is configured to apply an adjustable voltage V 1 to the inverting input terminal of the first operational amplifier, and a positive input terminal of the first operational amplifier is disconnected, the adjustable voltage is equal to a negative power supply voltage of the first operational amplifier VEE , and the device under test is in an off state; the follower sub-circuit is configured to apply the adjustable voltage V 1 to the inverting input terminal of the first operational amplifier, and a constant current source voltage is connected to the inverting input terminal of the first operational amplifier Vc 1 to the positive input terminal of the first operational amplifier, and the first operational amplifier outputs a modulation voltage, the modulation voltage is used to modulate the on-off rate of the device under test to control the voltage between the first electrode and the second electrode of the device under test V XY , so that V XY = Vc 1= V 1.

[0015] In some possible implementations, a second operational amplifier and a third operational amplifier are further included;

[0016] a non-inverting input terminal of the second operational amplifier is connected to the voltage control unit, an output terminal of the second operational amplifier is connected to an inverting input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is further connected to the inverting input terminal of the first operational amplifier;

[0017] a non-inverting input terminal of the third operational amplifier is connected to the first electrode, an inverting input terminal of the third operational amplifier is connected to an output terminal of the third operational amplifier, and the output terminal of the third operational amplifier is connected to a non-inverting input terminal of the first operational amplifier.

[0018] In some possible implementations, a second resistor is further connected in series between the non-inverting input terminal of the third operational amplifier and the first electrode of the device under test;

[0019] the inverting input terminal of the third operational amplifier and the output terminal of the third operational amplifier are connected in series through a third resistor;

[0020] The inverting input terminal of the second operational amplifier is connected in series with the output terminal of the second operational amplifier through a fourth resistor;

[0021] A fifth resistor is connected in series between the non-inverting input of the second operational amplifier and the voltage control unit.

[0022] In some possible implementations, the constant current source sub-circuit includes feedback and control loops. MOS Field-effect transistor, energy storage capacitor, and first resistor;

[0023] One end of the energy storage capacitor is connected to the first electrode of the device under test, and the other end of the energy storage capacitor is connected to the first resistor. MOS The second electrode of the field-effect transistor, the MOS The first terminal of the field-effect transistor is connected to the second terminal of the device under test;

[0024] One end of the feedback and control loop is connected to the MOS The second terminal of the field-effect transistor, and the other end of the feedback and control loop are connected to the second terminal of the device under test.

[0025] In some possible implementations, the test module includes a microcontroller. MCU and analog-to-digital converter ADC ;

[0026] The ADC Used to acquire the voltage between the first and second poles of the device under test;

[0027] The MCU Used to receive the ADC The voltage between the first and second terminals of the device under test (DUT) and the constant current source current of the constant current source circuit are collected to analyze and obtain the transconductance curve of the DUT.

[0028] In some possible implementations, a first switch is connected in series between the non-inverting input of the third operational amplifier and the first pole of the device under test, and the second pole of the device under test is grounded through a second switch.

[0029] Secondly, embodiments of the present invention provide a method for testing the transconductance curve of a transconductance curve testing circuit according to a first aspect of the present invention, comprising:

[0030] Before the transconductance test, disconnect the first switch and the second switch, and the voltage control unit inputs an adjustable voltage to the non-inverting input of the second operational amplifier. V 1. The second operational amplifier outputs a second output voltage. V 2 to the inverting input terminal of the first operational amplifier, andV 1= V 2. The first operational amplifier outputs a modulation voltage. V 4. Modulation voltage V 4 is equal to the negative power supply voltage of the first operational amplifier. VEE , V 4= VEE The voltage between the first and second terminals of the device under test V XY When the voltage is negative, the device under test is in an off state;

[0031] To begin the transconductance test, close the first and second switches, and the constant current source voltage... Vc 1 represents the input voltage at the non-inverting input terminal of the third operational amplifier, and the constant current source voltage is output as the third output voltage after passing through the third operational amplifier. V 3, V 3= Vc 1. The third output voltage V 3 is fed to the non-inverting input of the first operational amplifier, which operates in the linear region, and the first operational amplifier supplies the second output voltage. V 2 and the third input voltage V The voltage difference of 3 is processed by an operational amplifier to generate a modulation voltage. V 4. The modulation voltage V 4. The modulation voltage is input to the gate G of the device under test; V 4. To modulate the conduction of the device under test, the non-inverting and inverting inputs of the first operational amplifier are balanced to modulate the voltage between the first and second terminals of the device under test. V XY , V XY After being followed by the first operational amplifier, it makes V 2= V 3= V XY ;

[0032] The voltage between the gate and the second electrode of the device under test, as well as the current output by the constant current source circuit, are collected. The transconductance curve is determined based on the relationship curve between the voltage between the gate and the second electrode and the current output by the constant current source circuit.

[0033] Thirdly, embodiments of the present invention provide a transconductance curve testing system, the testing system including the transconductance curve testing circuit described in the first aspect of the present invention, and further including: a main chassis, a test head, and a device under test;

[0034] The modulation module and the constant current source sub-circuit in the test circuit are arranged on a resource board in the main box, the resource board is connected with the test head through a test cable, the test module in the test circuit is connected with the test head, and the test head is also connected with the device under test.

[0035] The beneficial effects of the above embodiment are that the constant current source voltage output from the constant current source sub-circuit to the first electrode of the device under test realizes the constant voltage state between the device under test, realizes the transconductance curve test, and does not need to use a feedback module to realize the measurement of the transconductance, thereby reducing the cost of the system. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0037] Figure 1 A schematic diagram of testing the parameters of a power device by a constant current source in the prior art;

[0038] Figure 2 A Vge transmission characteristic curve corresponding to different Ic currents when Vce=20V in the prior art;

[0039] Figure 3 A Vce output characteristic curve corresponding to different Ic currents when Vge=20V in the prior art;

[0040] Figure 4 An embodiment flowchart of a test circuit of a transconductance curve provided by the present application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0042] Some block diagrams shown in the drawings are functional entities, which do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different network and / or processor systems and / or microcontroller systems.

[0043] Reference to an "embodiment" in this document means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is expressly understood that the embodiments described herein can be combined with each other in their various permutations and combinations.

[0044] Figure 4 An embodiment of a test circuit for a transconductance curve of the application is shown in a flowchart as Figure 4 The test circuit includes a constant current source sub-circuit, a modulation module, and a test module.

[0045] One end of the constant current source sub-circuit is connected to a first pole of a device under test, the other end of the constant current source sub-circuit is connected to a second pole of the device under test, and the constant current source sub-circuit inputs a constant current source path current and a constant current source voltage to the device under test; wherein the first pole is a drain D, and the second pole is a source S, or the first pole is a collector C, and the second pole is an emitter E.

[0046] The modulation module includes a voltage control unit and a follower sub-circuit, the voltage control unit is used to output an adjustable voltage to the follower sub-circuit, the follower sub-circuit is connected to a gate G of the device under test, and the follower sub-circuit is used to generate a modulation voltage according to the adjustable voltage and the constant current source voltage, modulate the on rate of the device under test by the modulation voltage, control the voltage between the first pole and the second pole of the device under test, and make the voltage between the first pole and the second pole equal to the adjustable voltage.

[0047] The test module (not shown in the figure) is used to detect the voltage between the gate G and the second pole (collector E) of the device under test, and generate a transconductance curve according to the constant current source path current and the voltage between the gate and the second pole of the device under test.

[0048] In this embodiment, the device under test is a semiconductor power device including a first pole, a second pole, and a gate G, wherein the first pole is a drain D, and the second pole is a source S, or the first pole is a collector C, and the second pole is an emitter E; it can be an IGBT (Insulated Gate Bipolar Transistor) power device, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or a bipolar transistor. That is, the gate of the field effect transistor corresponds to the base of the transistor, and the source and drain of the field effect transistor correspond to the emitter and collector of the transistor.

[0049] Compared to existing technologies, this embodiment adds an external accessory module, namely a modulation module, to the constant current source equipment. This module utilizes the high-side output voltage of the constant current source to maintain a constant voltage across the first and second terminals of the device under test, enabling transconductance curve testing. This reduces the need for multiple devices when testing relevant parameters in power device systems, lowering the overall testing system cost. Furthermore, the module's small size and flexible operation make it more convenient.

[0050] Based on the above embodiments, as a preferred implementation method, as follows: Figure 4 As shown, with an IGBT power supply as the device under test, the constant current source circuit supplies current to the collector of the device under test. C Input constant current source voltage Vc 1;

[0051] The input terminal of the follower sub-circuit is connected to the IGBT collector of power device C And the voltage control unit, the output of the follower sub-circuit is connected to the IGBT gate of the power unit G ;

[0052] The follower sub-circuit includes a first operational amplifier. U 1. The first operational amplifier U The non-inverting input of 1 is connected to the IGBT collector of power device C The first operational amplifier U The inverting input terminal of 1 is connected to the voltage control unit;

[0053] The follower sub-circuit is used to apply an adjustable voltage before transconductance testing. V 1 as the first operational amplifier U The input to the inverting input terminal of the first operational amplifier is 1. U When the non-inverting input of 1 is disconnected, the modulation voltage is equal to that of the first operational amplifier. U 1 negative power supply voltage VEE The IGBT The power unit is in the off state; the follower sub-circuit is tested with the adjustable voltage during the transconductance test. V 1 as the first operational amplifier U The inverting input of 1 is connected to a constant current source voltage. Vc 1 as the first operational amplifier U The input to the non-inverting input terminal of the first operational amplifier is the modulation voltage output of the first operational amplifier. V 4. The modulation voltage is used to modulate the IGBT The conduction rate of the power unit is used to control the power supply. IGBT collector of power device C and emitterE voltage between V CE ,make V CE = Vc 1= V 1.

[0054] Based on the above embodiments, as a preferred implementation, a second operational amplifier is also included. U 2 and the third operational amplifier U 3;

[0055] Second operational amplifier U The non-inverting input terminal of 2 is connected to the voltage control unit, and the second operational amplifier... U The output of 2 is connected to the second operational amplifier. U The inverting input terminal of 2, the second operational amplifier U The output of 2 is also connected to the first operational amplifier. U The inverting input of 1;

[0056] The third operational amplifier U The non-inverting input terminal of 1 is connected to the collector C, and the third operational amplifier U The inverting input of 3 is connected to the third operational amplifier. U The output terminal of 3, the third operational amplifier U The output terminal of 3 is connected to the first operational amplifier. U The non-inverting input of 1.

[0057] Based on the above embodiments, as a preferred implementation, the third operational amplifier U The non-inverting input terminal of 3 is connected to the device under test ( IGBT The first electrode (collector) of the power unit C A second resistor is also connected in series between them. R 2;

[0058] The third operational amplifier U The inverting input terminal of 3 is connected to the third operational amplifier. U The output of 3 is connected in series with a third resistor. R 3;

[0059] Second operational amplifier U The inverting input of 2 is connected to the second operational amplifier. U The output of 2 is connected to the fourth resistor. R 4 in series;

[0060] Second operational amplifier U A fifth resistor is also connected in series between the non-inverting input terminal of 2 and the voltage control unit.R 5.

[0061] The third operational amplifier U The non-inverting input terminal of 3 is connected to the device under test ( IGBT The first electrode (collector) of the power unit C The first switch is connected in series between them. K 1. The second electrode of the device under test is also connected to a second switch. K 2. Grounding.

[0062] In this embodiment, VCC and VEE These are op-amps (first operational amplifier) U 1. Second operational amplifier U 2. Third operational amplifier U 3) The positive and negative power supply voltages, in this embodiment, are selected as follows: VCC =30 V , VEE =-5 V .

[0063] Using an IGBT power unit as the device under test, disconnect the first switch before transconductance testing. K 1 and the second switch K 2. The voltage control unit supplies power to the second operational amplifier. U The non-inverting input terminal of 2 receives an adjustable voltage. V 1. The second operational amplifier U 2. Output Second Output Voltage V 2 to the first operational amplifier U The inverting input of 1, and V 1= V 2. The first operational amplifier U 1 Output modulation voltage V 4. Modulation voltage V 4 equals the first operational amplifier U 1 negative power supply voltage VEE , V 4= VEE =-5 V The collector of the device under test C and emitter E voltage between V CE When the voltage is negative, the device under test is in an open state.

[0064] To begin the transconductance test, close the first switch. K 1 and the second switch K 2. The constant current source voltage Vc 1 is the third operational amplifier Uthe input voltage of the non-inverting input terminal of the third operational amplifier U 3 outputs the third output voltage V 3, at this time, V 3= Vc 1, the third output voltage V 3 is delivered to the first operational amplifier U 1, the non-inverting input terminal of the first operational amplifier U 1 works in linear region, the first operational amplifier U 1 to the second output voltage V 2 and the third input voltage V 3, the voltage difference is amplified to generate a modulation voltage V 4, the modulation voltage V 4 is input to the gate G of the IGBT power device; the modulation voltage V 4 is used to modulate the on rate of the IGBT power device, the first operational amplifier U 1, the non-inverting input terminal and the inverting input terminal of the first operational amplifier are balanced to modulate the voltage of the collector C and the emitter E of the IGBT power device V CE , V CE followed by the first operational amplifier U 1, so that V 2= V 3= V CE ;

[0065] the voltage between the gate and the second electrode of the device under test is collected V GE , and the current output by the constant current source sub-circuit, according to the voltage between the gate and the second electrode V GE , the current output by the constant current source sub-circuit, the transconductance curve is determined according to the relationship curve. Therefore, the constant V CE time, Ic = f ( V GE ) curve.

[0066] On the basis of the above embodiment, as a preferred embodiment, the constant current source sub-circuit comprises a feedback and control loop, MOS field effect transistor Q 1, energy storage capacitor C 1 and first resistor R 1;

[0067] the energy storage capacitor COne end of 1 is connected to the first electrode of the device under test, and the energy storage capacitor C The other end of 1 is connected to the first resistor. MOS Field-effect transistor Q The second pole of 1, the MOS Field-effect transistor Q The first electrode of 1 is connected to the second electrode of the device under test;

[0068] One end of the feedback and control loop is connected to the MOS Field-effect transistor Q The second pole of 1, the other end of the feedback and control loop is connected to the second pole of the device under test.

[0069] Based on the above embodiments, as a preferred implementation, the test module includes a microcontroller. MCU and analog-to-digital converter ADC ;

[0070] The ADC Used to acquire the voltage between the first and second poles of the device under test;

[0071] The MCU Used to receive the ADC The voltage between the first and second terminals of the device under test (DUT) and the constant current source current of the constant current source circuit are collected to analyze and obtain the transconductance curve of the DUT.

[0072] This invention provides a method for testing the transconductance curve of a transconductance curve testing circuit according to the above embodiments of the invention, comprising:

[0073] Using an IGBT power unit as the device under test, disconnect the first switch before transconductance testing. K 1 and the second switch K 2. The voltage control unit supplies power to the second operational amplifier. U The non-inverting input terminal of 2 receives an adjustable voltage. V 1. The second operational amplifier U 2. Output Second Output Voltage V 2 to the first operational amplifier U The inverting input of 1, and V 1= V 2. The first operational amplifier U 1 Output modulation voltage V 4. Modulation voltage V 4 equals the first operational amplifier U 1 negative power supply voltage VEE , V 4= VEE =-5V collector of the device under test C and the emitter E between the collector and the emitter V CE is negative, the device under test is in an off state;

[0074] starts a transconductance test, closes the first switch K 1 and the second switch K 2, the constant current source voltage Vc 1 is an input voltage of the non-inverting input terminal of the third operational amplifier U 3, the constant current source voltage is output as a third output voltage U 3 after passing through the third operational amplifier V 3, at this time, V 3= Vc 1, the third output voltage V 3 is transmitted to the non-inverting input terminal of the first operational amplifier U 1, the first operational amplifier U 1 works in a linear region, the first operational amplifier U 1 performs operational processing on a voltage difference between the second output voltage V 2 and the third input voltage V 3, generates a modulation voltage V 4, and inputs the modulation voltage V 4 to the gate G of the IGBT power device; the modulation voltage V 4 is used to modulate the on-off rate of the IGBT power device, the non-inverting input terminal and the inverting input terminal of the first operational amplifier U 1 are balanced, and the voltages of the collector C and the emitter E of the IGBT power device are modulated V CE , V CE followed by the first operational amplifier U 1, so that V 2= V 3= V CE ;

[0075] acquires the voltage between the gate and the second electrode of the device under test V GE , and the current output by the constant current source sub-circuit, determines a transconductance curve according to the relationship between the voltage between the gate and the second electrode V GE and the current output by the constant current source sub-circuit. Therefore, the constant time V CE , Ic = f ( VGE ) curve.

[0076] The test system of the transconductance curve provided by the embodiments of the present application comprises the test circuit of the transconductance curve of the above embodiments of the present application, and further comprises a host box, a test head and a device under test.

[0077] The modulation module and the constant current source sub-circuit in the test circuit are arranged on a resource board in the host box, the resource board is connected with the test head through a test cable, the test module in the test circuit is connected with the test head, and the test head is further connected with the device under test.

[0078] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiments can be completed by a computer program instructing relevant hardware (such as a processor, a controller, etc.) to complete, and the computer program can be stored in a computer readable storage medium. The computer readable storage medium is a disk, an optical disk, a read-only memory or a random access memory, etc.

[0079] The test circuit, the test method and the test system of the transconductance curve provided by the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples in this paper. The above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed, and the above description of the embodiments should not be understood as a limitation of the present application.

Claims

1. A test circuit for transconductance curves, characterized in that, The test circuit includes a constant current source sub-circuit, a modulation module, and a test module; One end of the constant current source sub-circuit is connected to the first terminal of the device under test, and the other end of the constant current source sub-circuit is connected to the second terminal of the device under test. The constant current source sub-circuit inputs a constant current source current and a constant current source voltage to the device under test. Wherein, the first terminal is the drain and the second terminal is the source, or the first terminal is the collector and the second terminal is the emitter. The modulation module includes a voltage control unit and a follower sub-circuit. The voltage control unit is used to output an adjustable voltage to the follower sub-circuit. The follower sub-circuit is connected to the gate of the device under test. The follower sub-circuit is used to generate a modulation voltage based on the adjustable voltage and the constant current source voltage. The modulation voltage modulates the conduction rate of the device under test to control the voltage between the first and second terminals of the device under test, so that the voltage between the first and second terminals is equal to the adjustable voltage. The test module is used to detect the voltage between the gate and the second electrode of the device under test, and to generate a transconductance curve based on the constant current source current and the voltage between the gate and the second electrode of the device under test. The constant current source sub-circuit includes a feedback and control loop. MOS Field-effect transistor, energy storage capacitor, and first resistor; One end of the energy storage capacitor is connected to the first electrode of the device under test, and the other end of the energy storage capacitor is connected to the first resistor. MOS The second electrode of the field-effect transistor, the MOS The first terminal of the field-effect transistor is connected to the second terminal of the device under test; One end of the feedback and control loop is connected to the MOS The second terminal of the field-effect transistor, and the other end of the feedback and control loop are connected to the second terminal of the device under test.

2. The test circuit for transconductance curves according to claim 1, characterized in that, The device under test includes an insulated gate bipolar transistor (IGBT) power device, a metal-oxide-semiconductor field-effect transistor (MOSFET), and a bipolar transistor.

3. The test circuit for transconductance curves according to claim 1, characterized in that, The constant current source sub-circuit inputs a constant current source voltage to the first terminal of the device under test. Vc 1; The input terminal of the follower sub-circuit is connected to the first electrode of the device under test and the voltage control unit, and the output terminal of the follower sub-circuit is connected to the gate of the device under test. The follower sub-circuit includes a first operational amplifier, the non-inverting input of which is connected to the first pole of the device under test, and the inverting input of which is connected to the voltage control unit. The follower sub-circuit is used to apply an adjustable voltage before transconductance testing. V 1 is used as the input to the inverting input of the first operational amplifier, the non-inverting input of the first operational amplifier is disconnected, and the modulation voltage is equal to the negative power supply voltage of the first operational amplifier. VEE The device under test is in the off state; the follower sub-circuit is tested with the adjustable voltage during transconductance testing. V 1 is used as the input to the inverting input of the first operational amplifier, and a constant current source voltage is connected. Vc 1 serves as the input to the non-inverting input of the first operational amplifier. The first operational amplifier outputs a modulation voltage, which is used to modulate the conduction of the device under test (DUT) to control the voltage between the first and second terminals of the DUT. V XY ,make V XY = Vc 1= V 1.

4. The test circuit for transconductance curves according to claim 3, characterized in that, It also includes a second operational amplifier and a third operational amplifier; The non-inverting input of the second operational amplifier is connected to the voltage control unit, the output of the second operational amplifier is connected to the inverting input of the second operational amplifier, and the output of the second operational amplifier is also connected to the inverting input of the first operational amplifier; The non-inverting input of the third operational amplifier is connected to the first pole, the inverting input of the third operational amplifier is connected to the output of the third operational amplifier, and the output of the third operational amplifier is connected to the non-inverting input of the first operational amplifier.

5. The test circuit for transconductance curves according to claim 4, characterized in that, A second resistor is connected in series between the non-inverting input terminal of the third operational amplifier and the first terminal of the device under test; The inverting input terminal of the third operational amplifier is connected in series with the output terminal of the third operational amplifier through a third resistor; The inverting input terminal of the second operational amplifier is connected in series with the output terminal of the second operational amplifier through a fourth resistor; A fifth resistor is connected in series between the non-inverting input of the second operational amplifier and the voltage control unit.

6. The test circuit for transconductance curves according to claim 1, characterized in that, The test module includes a microcontroller. MCU and analog-to-digital converter ADC ; The ADC Used to acquire the voltage between the first and second poles of the device under test; The MCU Used to receive the ADC The voltage between the first and second terminals of the device under test (DUT) and the constant current source current of the constant current source circuit are collected to analyze and obtain the transconductance curve of the DUT.

7. The test circuit for transconductance curves according to claim 4, characterized in that, A first switch is connected in series between the non-inverting input terminal of the third operational amplifier and the first terminal of the device under test, and the second terminal of the device under test is grounded through a second switch.

8. A method for testing the transconductance curve of a test circuit according to any one of claims 4, 5, and 7, characterized in that, include: Before the transconductance test, disconnect the first switch and the second switch, and the voltage control unit inputs an adjustable voltage to the non-inverting input of the second operational amplifier. V 1. The second operational amplifier outputs a second output voltage. V 2 to the inverting input terminal of the first operational amplifier, and V 1= V 2. The first operational amplifier outputs a modulation voltage. V 4. Modulation voltage V 4 is equal to the negative power supply voltage of the first operational amplifier. VEE , V 4= VEE The voltage between the first and second terminals of the device under test V XY When the voltage is negative, the device under test is in an open state. To begin the transconductance test, close the first and second switches, and the constant current source voltage... Vc 1 represents the input voltage at the non-inverting input terminal of the third operational amplifier, and the constant current source voltage is output as the third output voltage after passing through the third operational amplifier. V 3, V 3= Vc 1. The third output voltage V 3 is fed to the non-inverting input of the first operational amplifier, which operates in the linear region, and the first operational amplifier supplies the second output voltage. V 2 and third output voltage V The voltage difference of 3 is processed by an operational amplifier to generate a modulation voltage. V 4. The modulation voltage V 4. The modulation voltage is input to the gate G of the device under test; V 4. To modulate the conduction of the device under test, the non-inverting and inverting inputs of the first operational amplifier are balanced to modulate the voltage between the first and second terminals of the device under test. V XY , V XY After being followed by the first operational amplifier, it makes V 2= V 3= V XY ; The voltage between the gate and the second electrode of the device under test, as well as the current output by the constant current source circuit, are collected. The transconductance curve is determined based on the relationship curve between the voltage between the gate and the second electrode and the current output by the constant current source circuit.

9. A testing system for transconductance curves, characterized in that, The testing system includes the transconductance curve testing circuit of any one of claims 1 to 7, and further includes: a main chassis, a test head, and the device under test; The modulation module and constant current source sub-circuit in the test circuit are located on the resource board inside the main unit chassis. The resource board is connected to the test head via a test cable. The test module in the test circuit is connected to the test head, and the test head is also connected to the device under test.

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