Adjustable nanoampere-level constant current source circuit and test system

Abstract

The utility model discloses an adjustable nanoamp constant current source circuit and a test system, the adjustable nanoamp constant current source circuit comprises a precision reference source circuit, an operational amplifier feedback regulation circuit, a control circuit, an analog switch circuit and a junction field effect transistor, the analog switch circuit is respectively connected with the control circuit and the operational amplifier feedback regulation circuit, and the junction field effect transistor is connected with the operational amplifier feedback regulation circuit. And the operational amplifier feedback regulation circuit is also connected with the precise reference source circuit and the junction field effect transistor respectively. According to the utility model, the precise reference source circuit is adopted to provide a reference voltage source; the operational amplifier feedback regulation circuit performs voltage-current conversion on the reference voltage of the reference voltage source to generate a current source, and controls the junction field effect transistor to be conducted to output a constant current source; the control circuit is used for controlling the analog switch circuit to adjust the constant current source, the control circuit is used for controlling the analog switch circuit to achieve output adjustment of the constant current source, the junction field effect transistor is used for reducing leakage current, and therefore output precision of the nanoampere-level constant current source is improved, and high-precision measurement and testing are achieved.

Description

Technical Field

[0001] This utility model relates to the field of constant current source testing technology, and in particular to an adjustable nanoampere-level constant current source circuit and testing system. Background Technology

[0002] A constant current source circuit is a power supply that maintains a constant output current. It is widely used in resistance testing, capacitance testing, thermistor measurement, force sensor measurement, and magnetic sensor measurement. Compared to constant voltage measurement, constant current sources offer stronger anti-interference capabilities and longer transmission distances. However, nanoampere-level constant current source circuits use fixed resistors, making it impossible to adjust the output current. Furthermore, the output stage of nanoampere-level constant current source circuits uses switching MOSFETs or transistors to regulate the dynamic current. Due to the leakage current inherent in these switching components, nanoampere-level constant current sources suffer from poor accuracy, making high-precision measurement and testing difficult. Utility Model Content

[0003] The purpose of this invention is to design an adjustable nanoampere constant current source circuit to solve the above problems.

[0004] This utility model achieves the above objectives through the following technical solutions:

[0005] The adjustable nanoampere constant current source circuit includes:

[0006] The circuit includes a precision reference source circuit, an operational amplifier feedback adjustment circuit, a control circuit, an analog switch circuit, and a junction field-effect transistor. The control terminal of the control circuit is connected to the first terminal of the analog switch circuit, and the second terminal of the analog switch circuit is connected to the operational amplifier feedback adjustment circuit. The operational amplifier feedback adjustment circuit is also connected to the precision reference source circuit and the junction field-effect transistor, respectively.

[0007] The precision reference source circuit is used to provide a reference voltage source;

[0008] The operational amplifier feedback regulation circuit is used to convert the reference voltage of the reference voltage source into a voltage-to-current source, generate a current source, and control the junction field-effect transistor to conduct and output a constant current source.

[0009] The control circuit is used to control the analog switching circuit to adjust the constant current source output by the operational amplifier feedback adjustment circuit.

[0010] This invention also proposes a testing system, which includes the aforementioned adjustable nanoampere constant current source circuit.

[0011] The beneficial effects of this utility model are as follows:

[0012] The adjustable nanoampere constant current source circuit uses a precision reference source circuit to provide a stable, low-noise 2.5V reference voltage source. The operational amplifier feedback adjustment circuit converts the reference voltage of the reference voltage source into a voltage-to-current source to generate a current source and controls the junction field-effect transistor to conduct to output a constant current source. The control circuit controls the analog switching circuit to adjust the constant current source output by the operational amplifier feedback adjustment circuit. This invention uses a control circuit to control the analog switching circuit to achieve adjustment of different current outputs of the constant current source, and uses a junction field-effect transistor to reduce leakage current, thereby improving the output accuracy of the nanoampere constant current source and achieving high-precision measurement and testing. Attached Figure Description

[0013] Figure 1 This is an overall block diagram of the adjustable ampere-level constant current source circuit of this utility model;

[0014] In the diagram: 10 - Precision reference source circuit, 20 - Control circuit, 30 - Analog switch circuit, 40 - Operational amplifier feedback adjustment circuit, 50 - Junction field-effect transistor, 60 - Power supply circuit. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0017] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0018] In the description of this utility model, it should be understood that the terms "upper", "lower", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use, or the orientation or positional relationship that is commonly understood by those skilled in the art. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0019] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0020] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0021] The specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, the adjustable ampere-level constant current source circuit includes:

[0023] The circuit includes a precision reference source circuit 10, an operational amplifier feedback adjustment circuit 40, a control circuit 20, an analog switch circuit 30, and a junction field-effect transistor 50. The control terminal of the control circuit 20 is connected to the first terminal of the analog switch circuit 30, and the second terminal of the analog switch circuit 30 is connected to the operational amplifier feedback adjustment circuit 40. The operational amplifier feedback adjustment circuit 40 is also connected to the precision reference source circuit 10 and the junction field-effect transistor 50, respectively.

[0024] The precision reference source circuit 10 is used to provide a reference voltage source;

[0025] The operational amplifier feedback adjustment circuit 40 is used to convert the reference voltage of the reference voltage source into a voltage-to-current source, generate a current source, and control the junction field-effect transistor 50 to conduct and output a constant current source.

[0026] The control circuit 20 is used to control the analog switch circuit 30 to adjust the constant current source output by the operational amplifier feedback adjustment circuit 40.

[0027] In this embodiment, the precision reference source circuit 10 can be implemented using an ADR431, which has high initial output voltage accuracy and extremely low temperature drift; the operational amplifier feedback adjustment circuit 40 is implemented using an operational amplifier and a feedback resistor to convert the reference voltage of the reference voltage source into a voltage-to-current source; the control circuit 20 can be implemented using MCU (Microcontroller Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), SOC (System on Chip), etc.; the analog switch circuit 30 can be implemented using an optocoupler switch or CMOS (Complementary Metal Oxide Semiconductor), etc.; the junction field-effect transistor 50 is used as the constant current source output control, with extremely low leakage current, below 1 nanoamp at room temperature, thereby improving the output accuracy of the nanoamp-level constant current source.

[0028] This utility model's adjustable nanoampere constant current source circuit employs a precision reference source circuit 10 to provide a stable, low-noise 2.5V reference voltage source; the operational amplifier feedback adjustment circuit 40 converts the reference voltage of the reference voltage source into a voltage-to-current source to generate a current source, and controls the junction field-effect transistor 50 to conduct to output a constant current source; the control circuit 20 controls the analog switch circuit 30 to adjust the constant current source output by the operational amplifier feedback adjustment circuit 40. This utility model uses the control circuit 20 to control the analog switch circuit 30 to achieve adjustment of different current outputs of the constant current source, and uses the junction field-effect transistor 50 to reduce leakage current, thereby improving the output accuracy of the nanoampere constant current source, and thus achieving high-precision measurement and testing.

[0029] In one embodiment, the control circuit 20 includes a microcontroller, and the I / O port of the microcontroller is connected to the analog switch circuit 30.

[0030] Furthermore, the microcontroller is an STM32F407 chip.

[0031] In this embodiment, the control circuit 20 uses an embedded microcontroller to control different current sources. The microcontroller is an STM32F407 with a Cortex-M4 core architecture and a core operating frequency of up to 168MHz. The microcontroller has multiple communication peripheral interfaces such as SPI, serial port, and IIC. The microcontroller's I / O ports are connected to the analog switch circuit 30 to control the analog switch circuit 30 to switch different feedback resistors, thereby adjusting the magnitude of the output current source.

[0032] In one embodiment, the operational amplifier feedback adjustment circuit 40 includes an operational amplifier and a plurality of feedback resistors. The input terminal of the operational amplifier is connected to the precision reference source circuit 10, the output terminal of the operational amplifier is connected to the first terminal of each of the feedback resistors, the second terminal of each of the feedback resistors is connected to the junction field-effect transistor 50, and each of the feedback resistors is also connected to the second terminal of the analog switch circuit 30.

[0033] The analog switch circuit 30 is used to switch multiple feedback resistors and adjust the current source output by the feedback resistors.

[0034] Furthermore, the operational amplifier is a TLV272 chip.

[0035] In this embodiment, the operational amplifier performs voltage-to-current conversion on the reference voltage source output by the precision reference circuit to generate a current source. The control circuit 20 controls the on / off state of the analog switch circuit 30 and switches different feedback resistors to adjust the output current. The operational amplifier is implemented using a TLV272 chip, and the rail-to-rail operational amplifier has extremely low input bias voltage and input bias current.

[0036] In one embodiment, the adjustable nanoampere constant current source circuit further includes a power supply circuit 60 for providing operating power.

[0037] In this embodiment, the power supply circuit 60 uses a switching power supply plus a low-noise linear power supply to provide the entire circuit with a low-noise, positive and negative stable operating power supply.

[0038] This utility model also proposes a testing system, which includes the above-described adjustable nanoampere constant current source circuit; the specific structure of the adjustable nanoampere constant current source circuit is as described in the above embodiments. Since this testing system adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0039] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. An adjustable nanoampere-level constant current source circuit, characterized in that, The adjustable nanoampere constant current source circuit includes: The circuit includes a precision reference source circuit, an operational amplifier feedback adjustment circuit, a control circuit, an analog switch circuit, and a junction field-effect transistor. The control terminal of the control circuit is connected to the first terminal of the analog switch circuit, and the second terminal of the analog switch circuit is connected to the operational amplifier feedback adjustment circuit. The operational amplifier feedback adjustment circuit is also connected to the precision reference source circuit and the junction field-effect transistor, respectively. The precision reference source circuit is used to provide a reference voltage source; The operational amplifier feedback regulation circuit is used to convert the reference voltage of the reference voltage source into a voltage-to-current source, generate a current source, and control the junction field-effect transistor to conduct and output a constant current source. The control circuit is used to control the analog switching circuit to adjust the constant current source output by the operational amplifier feedback adjustment circuit.

2. The adjustable ampere-ampere constant current source circuit according to claim 1, characterized in that, The control circuit includes a microcontroller, and the microcontroller's I / O ports are connected to the analog switch circuit.

3. The adjustable ampere-level constant current source circuit according to claim 2, characterized in that, The microcontroller is an STM32F407 chip.

4. The adjustable ampere-level constant current source circuit according to claim 1, characterized in that, The operational amplifier feedback adjustment circuit includes an operational amplifier and multiple feedback resistors. The input terminal of the operational amplifier is connected to the precision reference source circuit, the output terminal of the operational amplifier is connected to the first terminal of each feedback resistor, the second terminal of each feedback resistor is connected to the junction field-effect transistor, and each feedback resistor is also connected to the second terminal of the analog switch circuit. The analog switch circuit is used to switch multiple feedback resistors and adjust the current source output by the feedback resistors.

5. The adjustable ampere-ampere constant current source circuit according to claim 4, characterized in that, The operational amplifier is a TLV272 chip.

6. The adjustable ampere-ampere constant current source circuit according to claim 1, characterized in that, The adjustable nanoampere constant current source circuit also includes a power supply circuit, which is used to provide operating power.

7. A testing system, characterized in that, The test system includes an adjustable nanoampere constant current source circuit as described in any one of claims 1-6.

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