A method and circuit for generating microcurrent

Abstract

This invention discloses a method and circuit for generating a microcurrent. It includes: using a high-impedance voltage follower to convert the working electrode voltage in the input terminal into a working voltage with a reference potential VCOM as the reference point; applying the input voltage Vin to the inverting input of an adder, and connecting the working voltage converted by the voltage follower to the non-inverting input of the adder to obtain an output voltage Vo; connecting the output voltage and the working voltage across a standard conversion resistor to obtain an output microcurrent. This method enables a very high resistance between the microcurrent generating circuit and the working electrode WE of the tool (such as an electrochemical workstation), resulting in very low leakage current and thus obtaining a highly accurate standard microcurrent independent of the reference potential VCOM.

Description

Technical Field

[0001] This invention relates to the field of microcurrent technology, and in particular to a method and circuit for generating microcurrent. Background Technology

[0002] Microcurrent refers to direct current less than 1 microamp. Its operating range is from 0.5 nA to 1 μA, with an output resistance of approximately 2 MΩ, a relative accuracy of ±0.1% (i.e., minimum current error less than ±0.5 pA), and an operating ambient temperature of 10–30℃ and humidity less than 80% RH. In recent years, various electrochemical sensors based on microcurrent measurement have been increasingly applied in fields such as biology, chemistry, and medicine. Electrochemical workstations are currently the primary tools for measuring microcurrents. However, calibrating these tools through traceability is a common challenge. There are currently no relevant metrological standards, and a lack of dedicated equipment to calibrate microcurrent measurement tools. This results in significant errors in the accuracy and consistency of electrochemical sensors, introducing considerable uncertainty into scientific research and clinical monitoring. The root cause of this situation is that when using traditional methods to generate microcurrents as a standard current source, the measuring tool itself is prone to noise interference with the current source when measured using tools (such as electrochemical workstations), and a common-mode voltage exists between the measuring tool and the instrument used, leading to inaccurate measurement results. The technical challenge of microcurrent generating circuits lies in how to reduce circuit noise and leakage current in auxiliary circuits.

[0003] Traditional methods for generating microcurrents include: (1) using a V / I conversion circuit to directly generate current output, and (2) using a high-precision power supply and standard resistors to generate microcurrents. Among these, (1) using a V / I conversion circuit to directly generate current output is as follows: Figure 1 As shown, Figure 1In this circuit, R1 / R3 = R2 / R4. When R1 = R2 = R3 = R4, then Io = Vi / Rs. This circuit is often used for V / I conversion and is widely used in current generation applications. However, the load resistance has a significant impact on this circuit, and the nonlinear error is relatively large. A feedback tracking circuit is often required to form a closed-loop regulation to control the accuracy of the current output. Furthermore, since Rs is much smaller than R1, R2, R3, and R4, obtaining a small current inevitably requires reducing the input voltage Vi. This inevitably introduces operational errors in the step-down circuit, further reducing the overall accuracy of the current output. Additionally, this circuit requires one or two transistors (or MOSFETs) to participate in the conversion, which also introduces leakage current errors and more noise interference. Noise interference is the most intolerable factor in small current generators and has the greatest impact on the accuracy of the current output. In this circuit, in addition to the noise caused by excessive voltage division of Vi, the noise caused by excessive R1, R2, R3, and R4, and the noise generated by transistor adjustment, there are also current errors caused by changes in load resistance and errors caused by the regulation rate of the op-amp and transistor. Therefore, this circuit is usually used in relatively large current applications above milliamp, and is not suitable for current generation applications below microamp. (2) Methods for generating small currents using high-precision power supplies and standard resistors, such as Figure 2 As shown, a high-precision voltage source and a standard resistor are used to generate a standard current. The basic principle is as follows: the common terminal of the standard voltage source is connected to the common terminal of the electrochemical workstation. The output voltage of the standard voltage source is Vo = V_set + V_COM - V_WE, and the output current is Io = Vo / Rs. When V_COM = V_WE, Io = V_set / Rs. Here, V_COM can also be called the common-mode voltage. Because this method is relatively simple, it is often used in practice to calibrate the accuracy of the electrochemical workstation. However, according to the above principle, when the common-mode voltage V_COM is not equal to V_WE, the magnitude of Io cannot be controlled. To obtain an accurate Io, it is necessary to accurately measure the difference between V_COM and V_WE and iterate this value into the V_set value to obtain the desired current value. Obviously, this method is too complex and cannot be applied to all electrochemical workstations, lacking universality. Summary of the Invention

[0004] To address the above problems, the present invention provides a microcurrent generation method and circuit.

[0005] In a first aspect, embodiments of the present invention provide a microcurrent generation method, comprising:

[0006] A high-impedance voltage follower is used to convert the working electrode voltage in the input terminal into a working voltage with the reference voltage as the reference point.

[0007] The input voltage is connected to the inverting terminal of the adder, and the operating voltage is connected to the non-inverting terminal of the adder to obtain the output voltage;

[0008] The output voltage and operating voltage are connected to the two ends of a standard conversion resistor respectively to obtain an output micro-current.

[0009] In some specific embodiments, the high-impedance voltage follower includes:

[0010] The system comprises a first operational amplifier, a second operational amplifier, a fourth operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first compensation resistor, and a second compensation resistor. The working electrode voltage of the input terminal is connected to the first terminal of a high-impedance voltage follower. The first terminal of the high-impedance voltage follower is connected to the first terminals of the first and fifth resistors. The second terminal of the first resistor is connected to the inverting input of the first operational amplifier and the first terminal of the second resistor. The second terminal of the second resistor is connected to the output terminal of the first operational amplifier and the first terminal of the third resistor. The non-inverting input of the first operational amplifier is connected to the first terminal of the first compensation resistor. The second terminal of the first compensation resistor is connected to the first terminal of the second compensation resistor. The second terminal of the second compensation resistor is connected to the non-inverting input of the second operational amplifier. The second terminal of the third resistor is connected to the first terminal of the fourth resistor and the inverting input of the second operational amplifier. The second terminal of the fifth resistor is connected to the second terminal of the fourth resistor, the output terminal of the second operational amplifier, and the non-inverting input of the fourth operational amplifier. The second terminal of the high-impedance voltage follower is connected to the non-inverting input of the adder, the output terminal of the fourth operational amplifier, and the inverting input.

[0011] In some specific embodiments, the first resistor, the second resistor, the third resistor, and the fifth resistor have the same resistance value, and the resistance value of the fourth resistor is twice that of the first resistor.

[0012] In some specific embodiments, the adder includes:

[0013] The sixth resistor, the seventh resistor, the eighth resistor, the ninth resistor, and the third operational amplifier;

[0014] The second terminal of the high-impedance voltage follower is connected to the non-inverting terminal of the adder. The non-inverting terminal of the adder is connected to the first terminal of the eighth resistor. The second terminal of the eighth resistor is connected to the first terminal of the ninth resistor and the non-inverting terminal of the third operational amplifier. The inverting terminal of the third operational amplifier is connected to the first terminal of the seventh resistor and the second terminal of the sixth resistor. The first terminal of the sixth resistor is connected to the output terminal of the third operational amplifier and the output terminal of the adder. The second terminal of the seventh resistor is connected to the inverting terminal of the adder.

[0015] In some specific embodiments, the seventh resistor and the eighth resistor have the same resistance value, the sixth resistor and the ninth resistor have the same resistance value, and the resistance value of the seventh resistor is twice that of the sixth resistor.

[0016] In some specific embodiments, the input voltage is a specific voltage value output by a digital-to-analog converter.

[0017] In some specific embodiments, the first operational amplifier, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier are all dual operational amplifiers.

[0018] Secondly, embodiments of the present invention provide a microcurrent generating circuit, comprising:

[0019] Adder, high-impedance voltage follower, and standard switching resistor;

[0020] The working electrode voltage in the input terminal is connected to the first terminal of the high impedance voltage follower and the first terminal of the standard conversion resistor, respectively. The second terminal of the high impedance voltage follower is connected to the non-inverting terminal of the adder. The input voltage is connected to the inverting terminal of the adder. The output terminal of the adder is connected to the second terminal of the standard conversion resistor.

[0021] The high-impedance voltage follower includes: a first operational amplifier, a second operational amplifier, a fourth operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first compensation resistor, and a second compensation resistor; the working electrode voltage in the input terminal is connected to the first terminal of the high-impedance voltage follower; the first terminal of the high-impedance voltage follower is connected to the first terminal of the first resistor and the first terminal of the fifth resistor respectively; the second terminal of the first resistor is connected to the inverting input of the first operational amplifier and the first terminal of the second resistor respectively; the second terminal of the second resistor is connected to the output terminal of the first operational amplifier and the first terminal of the third resistor respectively; the non-inverting input of the first operational amplifier is connected to the first terminal of the first compensation resistor; the second terminal of the first compensation resistor is connected to the first terminal of the second compensation resistor; the second terminal of the second compensation resistor is connected to the non-inverting input of the second operational amplifier; the second terminal of the third resistor is connected to the first terminal of the fourth resistor and the inverting input of the second operational amplifier respectively; the second terminal of the fifth resistor is connected to the second terminal of the fourth resistor, the output terminal of the second operational amplifier, and the non-inverting input of the fourth operational amplifier respectively; the second terminal of the high-impedance voltage follower is connected to the non-inverting input of the adder, the output terminal of the fourth operational amplifier, and the inverting input respectively.

[0022] The adder includes: a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, and a third operational amplifier; the second terminal of the high-impedance voltage follower is connected to the non-inverting input of the adder, the non-inverting input of the adder is connected to the first terminal of the eighth resistor, the second terminal of the eighth resistor is connected to the first terminal of the ninth resistor and the non-inverting input of the third operational amplifier, the inverting input of the third operational amplifier is connected to the first terminal of the seventh resistor and the second terminal of the sixth resistor, the first terminal of the sixth resistor is connected to the output terminal of the third operational amplifier and the output terminal of the adder, and the second terminal of the seventh resistor is connected to the inverting input of the adder.

[0023] In some specific embodiments, the first, second, third, and fifth resistors have the same resistance value, the fourth resistor has a resistance value twice that of the first resistor, the seventh and eighth resistors have equal resistance values, the sixth and ninth resistors have equal resistance values, and the seventh resistor has a resistance value twice that of the sixth resistor.

[0024] In some specific embodiments, the first operational amplifier, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier are all dual operational amplifiers.

[0025] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0026] By adding a high-impedance voltage follower, the resistance between the micro-current generating circuit and the working electrode (WE) of the tool (such as an electrochemical workstation) is made very large, resulting in extremely low leakage current and very high accuracy in micro-current generation. Furthermore, since the reference potential VCOM only serves as a synchronization reference and is independent of the relationship between the working electrode (WE) voltage and VCOM, a conveniently calculated standard current value can be generated regardless of whether the reference potential VCOM is equal to the working electrode (WE) voltage. The operational amplifiers used are all dual operational amplifiers, which ensures good consistency and cancels out the input offset voltage and the non-inverting input bias current. The leakage current depends on the accuracy of the first to fifth resistors and the consistency of the operational amplifiers, while the noise depends entirely on the 0.1Hz to 10Hz voltage input noise of the operational amplifiers. Therefore, this solution offers a wider selection of operational amplifiers and better practicality, especially given the current shortage and high price of high-end chips, which provides it with unique application opportunities. In addition, the small mesh size of the circuit during PCB fabrication makes it easy to create equipotential protection rings, preventing leakage current caused by excessive voltage differences, which could lead to excessive noise in the circuit.

[0027] Other features and advantages of the invention will be set forth in the following description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, but do not constitute a limitation on the technical solutions of the present invention. In the drawings:

[0030] Figure 1 The topology diagram for the direct output current of the V / I conversion circuit in traditional microcurrent generation methods;

[0031] Figure 2 This is a schematic diagram of the current source in the standard voltage source method of traditional microcurrent generation methods;

[0032] Figure 3 This is a topology diagram of a microcurrent generating circuit in an embodiment of the present invention;

[0033] Figure 4 This is another microcurrent generation circuit topology diagram in an embodiment of the present invention. Detailed Implementation

[0034] Exemplary embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that the technical solutions of the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0035] To address the problems existing in the prior art, embodiments of the present invention provide a microcurrent generation method and circuit.

[0036] Example 1

[0037] Embodiment 1 of the present invention provides a microcurrent generation method, comprising the following steps:

[0038] A high-impedance voltage follower is used to convert the working electrode voltage in the input terminal into a working voltage with the reference potential as the reference point. Using a high-impedance voltage follower circuit can minimize current leakage and convert the working electrode voltage in the input terminal into a working voltage with the reference potential as the reference point without loss.

[0039] The input voltage is connected to the inverting terminal of the adder, and the operating voltage is connected to the non-inverting terminal of the adder to obtain the output voltage;

[0040] The output voltage and operating voltage are connected to the two ends of a standard conversion resistor respectively to obtain a small output current. The output current value Io = (output voltage - operating voltage) / standard conversion resistor.

[0041] In some specific embodiments, such as Figure 3 As shown, the voltage at the input terminal WE (working electrode) is converted into a voltage Vwe in the micro-current generating circuit with the reference voltage VCOM as the reference point by a voltage follower. This voltage value (Vwe) is equal to the difference between the working electrode (WE) and VCOM, but the resistance between the working electrode (WE) and the voltage Vwe is very large (>10). 10The current absorption is extremely small (Ω), theoretically reaching zero current absorption. This ensures that the analog output current can be infinitely close to the theoretically calculated value; therefore, this scheme is also called a high-impedance precision current generator. The reference voltage is a voltage in a circuit that remains constant regardless of the load, power supply, temperature drift, time, etc. Reference voltages can be used in voltage regulators of power supply systems, analog-to-digital converters and digital-to-analog converters, as well as many other measurement and control systems. Figure 3 In this circuit, Vin is a specific voltage value output from the D / A (digital-to-analog converter). This voltage is added to Vwe at the inverting and non-inverting inputs of the adder to obtain the output voltage Vo, where Vo = Vwe - Vin. Vo and the working electrode (WE) voltage Vwe act across the standard switching resistor Rs, resulting in the output current Io. Since the working electrode (WE) voltage is equal to Vwe, Io = (Vo - Vwe) / Rs, therefore Io = -Vin / Rs.

[0042] In some specific embodiments, the high-impedance voltage follower includes:

[0043] First operational amplifier, second operational amplifier, fourth operational amplifier, first resistor, second resistor, third resistor, fourth resistor, fifth resistor, first compensation resistor and second compensation resistor;

[0044] The working electrode voltage in the input terminal is connected to the first terminal of the high-impedance voltage follower. The first terminal of the high-impedance voltage follower is connected to the first terminal of the first resistor and the first terminal of the fifth resistor. The second terminal of the first resistor is connected to the inverting terminal of the first operational amplifier and the first terminal of the second resistor. The second terminal of the second resistor is connected to the output terminal of the first operational amplifier and the first terminal of the third resistor. The non-inverting terminal of the first operational amplifier is connected to the first terminal of the first compensation resistor. The second terminal of the first compensation resistor is connected to the first terminal of the second compensation resistor. The second terminal of the second compensation resistor is connected to the non-inverting terminal of the second operational amplifier. The second terminal of the third resistor is connected to the first terminal of the fourth resistor and the inverting terminal of the second operational amplifier. The second terminal of the fifth resistor is connected to the second terminal of the fourth resistor, the output terminal of the second operational amplifier, and the non-inverting terminal of the fourth operational amplifier. The second terminal of the high-impedance voltage follower is connected to the non-inverting terminal of the adder, the output terminal of the fourth operational amplifier, and the inverting terminal.

[0045] In some specific embodiments, the first resistor, the second resistor, the third resistor, and the fifth resistor have the same resistance value, and the resistance value of the fourth resistor is twice that of the first resistor.

[0046] In some specific embodiments, the adder includes:

[0047] The sixth resistor, the seventh resistor, the eighth resistor, the ninth resistor, and the third operational amplifier;

[0048] The second terminal of the high-impedance voltage follower is connected to the non-inverting terminal of the adder. The non-inverting terminal of the adder is connected to the first terminal of the eighth resistor. The second terminal of the eighth resistor is connected to the first terminal of the ninth resistor and the non-inverting terminal of the third operational amplifier. The inverting terminal of the third operational amplifier is connected to the first terminal of the seventh resistor and the second terminal of the sixth resistor. The first terminal of the sixth resistor is connected to the output terminal of the third operational amplifier and the output terminal of the adder. The second terminal of the seventh resistor is connected to the inverting terminal of the adder.

[0049] In some specific embodiments, the seventh resistor and the eighth resistor have the same resistance value, the sixth resistor and the ninth resistor have the same resistance value, and the resistance value of the seventh resistor is twice that of the sixth resistor.

[0050] In some specific embodiments, the input voltage is a specific voltage value output by a digital-to-analog converter.

[0051] In some specific embodiments, the first operational amplifier, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier are all dual operational amplifiers.

[0052] In some specific embodiments, the microcurrent generating circuit is specifically as follows: Figure 4 As shown, operational amplifiers A1, A2 and A4, along with resistors R1, R2, R3, R4, R5, Rp1 and Rp2, constitute a high-impedance voltage follower. Its function is to convert the working electrode (WE) voltage into Vr and ensure that the voltage follower's sink current is 0, so as not to cause errors beyond the range to the analog output current Io.

[0053] Figure 4 middle:

[0054] 1. Resistors R1 = R2 = R3 = R5, R4 = 2R1;

[0055] 2. Rp1 and Rp2 are compensation resistors. They are used when the operational amplifier is powered by a single power supply to eliminate the voltage offset caused by the op-amp IB.

[0056] 3. Operational amplifier A3, together with R6, R7, R8 and R9, forms an adder, where R7 = R8, R6 = R9, and R7 = 2R6;

[0057] 4. Except for Rp1 and Rp2, the accuracy of all resistors in the circuit is better than 0.05%, and the temperature drift is better than 10PPM;

[0058] 5. The operational amplifier in the diagram is a high-precision, low-temperature-drift dual operational amplifier (such as ADA4522, OPA2392, or similar operational amplifiers). The advantage of using dual operational amplifiers is that the parameters of the two operational amplifiers in the circuit are basically the same, so that the standard current generated by the micro-current generating circuit is consistent with the theoretically calculated value.

[0059] Figure 4 In the circuit, the voltage Vwe at the working electrode (WE) is passed through an inverting amplifier A1 to obtain voltage V1A. Since R1 = R2, V1A = -Vwe. The input current of the inverting amplifier is I1. Then, V1A is passed through an inverting amplifier A2 to obtain voltage V2A. Since R4 = 2R3, V2A = -2V1A. Since R5 = R1, If ​​= (V2A - Vwe) / R5 = -I1, that is, If + I1 = 0. From this, it can be seen that this high-impedance voltage follower circuit will not affect the output (or input) current. However, a single op-amp voltage follower without this treatment will affect Io because the input bias current IB at the non-inverting input of the op-amp is not zero (such as op-amp A4), and cannot be used in high-precision current generators. Adder A3 adds the D / A output voltage Vin and the voltage V2A obtained through the voltage follower to the voltage Vr obtained after isolation by A4, to obtain the output voltage Vo. Since R7 = R8, R6 = R9, and R7 = 2R6, Vo = (Vr - Vin) / 2, thus simulating the output current Io = (Vo - Vwe) / Rs.

[0060] Figure 4 The scheme shown is the same as Figure 1 Compared to the method described above, the linearity of the current is better. The current output is only related to Vin and RS, and there are no other components that affect the accuracy of the current output. Furthermore, the resistors R6, R7, R8, R9 and the operational amplifier A3 form an adder, which has no constraint relationship with the standard conversion resistor Rs. Therefore, the resistance value of Rs can be adjusted according to the range of the micro-current.

[0061] Figure 4 The scheme shown is the same as Figure 2 Compared to the previous method, this scheme adds a voltage follower, resulting in a very high resistance between the microcurrent generating circuit and the working electrode (WE) of the tool (such as an electrochemical workstation), leading to very low leakage current and very high accuracy in microcurrent generation. Furthermore, since the VCOM terminal only serves as a synchronization reference potential and is independent of the relationship between the working electrode (WE) voltage and VCOM, a conveniently calculated standard current value can be generated regardless of whether VCOM and the working electrode (WE) voltage are equal.

[0062] In addition, such as Figure 4As shown, since A1, A2, A3, and A4 are all dual operational amplifiers, they can ensure good consistency of the op-amps to a certain extent, and can cancel out the input offset voltage, Vos, and the non-inverting input bias current IB. In addition, the small mesh size of the circuit during PCB fabrication makes it easy to create equipotential protection rings to prevent leakage current caused by excessive voltage differences, which could lead to excessive noise in the circuit.

[0063] In the method described in this embodiment, by adding a high-impedance voltage follower, the resistance between the micro-current generating circuit and the working electrode (WE) of the tool (such as an electrochemical workstation) is very large, resulting in very low leakage current and very high micro-current generation accuracy. Furthermore, since the reference potential VCOM only serves as a synchronization reference potential and is independent of the relationship between the working electrode (WE) voltage and VCOM, a conveniently calculated standard current value can be generated regardless of whether the reference potential VCOM is equal to the working electrode (WE) voltage. The operational amplifiers used are all dual operational amplifiers, which can ensure good consistency to a certain extent and cancel out the input offset voltage and the non-inverting input bias current. The leakage current depends on the accuracy of the first to fifth resistors and the consistency of the operational amplifiers, while the noise depends entirely on the 0.1Hz to 10Hz voltage input noise of the operational amplifiers. Therefore, this solution offers a wider selection of operational amplifiers and better practicality, especially given the current shortage and high price of high-end chips, which provides it with unique application opportunities. In addition, the small mesh size of the circuit during PCB fabrication makes it easy to create equipotential protection rings, preventing leakage current caused by excessive voltage differences, which could lead to excessive noise in the circuit.

[0064] Those skilled in the art can change the above order without departing from the scope of protection of this invention.

[0065] Example 2

[0066] Embodiment 2 of the present invention provides a microcurrent generating circuit, such as Figure 3 or Figure 4 As shown, it includes:

[0067] Adder, high-impedance voltage follower, and standard switching resistor;

[0068] The working electrode voltage in the input terminal is connected to the first terminal of the high impedance voltage follower and the first terminal of the standard conversion resistor, respectively. The second terminal of the high impedance voltage follower is connected to the non-inverting terminal of the adder. The input voltage is connected to the inverting terminal of the adder. The output terminal of the adder is connected to the second terminal of the standard conversion resistor.

[0069] The high-impedance voltage follower includes: a first operational amplifier, a second operational amplifier, a fourth operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first compensation resistor, and a second compensation resistor; the working electrode voltage in the input terminal is connected to the first terminal of the high-impedance voltage follower; the first terminal of the high-impedance voltage follower is connected to the first terminal of the first resistor and the first terminal of the fifth resistor respectively; the second terminal of the first resistor is connected to the inverting input of the first operational amplifier and the first terminal of the second resistor respectively; the second terminal of the second resistor is connected to the output terminal of the first operational amplifier and the first terminal of the third resistor respectively; the non-inverting input of the first operational amplifier is connected to the first terminal of the first compensation resistor; the second terminal of the first compensation resistor is connected to the first terminal of the second compensation resistor; the second terminal of the second compensation resistor is connected to the non-inverting input of the second operational amplifier; the second terminal of the third resistor is connected to the first terminal of the fourth resistor and the inverting input of the second operational amplifier respectively; the second terminal of the fifth resistor is connected to the second terminal of the fourth resistor, the output terminal of the second operational amplifier, and the non-inverting input of the fourth operational amplifier respectively; the second terminal of the high-impedance voltage follower is connected to the non-inverting input of the adder, the output terminal of the fourth operational amplifier, and the inverting input respectively.

[0070] The adder includes: a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, and a third operational amplifier; the second terminal of the high-impedance voltage follower is connected to the non-inverting input of the adder, the non-inverting input of the adder is connected to the first terminal of the eighth resistor, the second terminal of the eighth resistor is connected to the first terminal of the ninth resistor and the non-inverting input of the third operational amplifier, the inverting input of the third operational amplifier is connected to the first terminal of the seventh resistor and the second terminal of the sixth resistor, the first terminal of the sixth resistor is connected to the output terminal of the third operational amplifier and the output terminal of the adder, and the second terminal of the seventh resistor is connected to the inverting input of the adder.

[0071] In some specific embodiments, the first, second, third, and fifth resistors have the same resistance value, the fourth resistor has a resistance value twice that of the first resistor, the seventh and eighth resistors have equal resistance values, the sixth and ninth resistors have equal resistance values, and the seventh resistor has a resistance value twice that of the sixth resistor.

[0072] In some specific embodiments, the first operational amplifier, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier are all dual operational amplifiers.

[0073] In this embodiment, by adding a high-impedance voltage follower, the resistance between the micro-current generating circuit and the working electrode (WE) of the tool (such as an electrochemical workstation) is made very large, resulting in very low leakage current and very high micro-current generation accuracy. Furthermore, since the reference potential VCOM only serves as a synchronization reference potential and is independent of the relationship between the working electrode (WE) voltage and VCOM, a conveniently calculated standard current value can be generated regardless of whether the reference potential VCOM is equal to the working electrode (WE) voltage. The operational amplifiers used are all dual operational amplifiers, which can ensure good consistency among the operational amplifiers to a certain extent, and can cancel out the input offset voltage and the non-inverting input bias current. The leakage current depends on the accuracy of the first to fifth resistors and the consistency of the operational amplifiers, while the noise depends entirely on the voltage input noise of the operational amplifiers from 0.1Hz to 10Hz. Therefore, this solution offers a wider selection of operational amplifiers and better practicality, especially given the current shortage and high price of high-end chips, which provides it with unique application opportunities. In addition, the small mesh size of the circuit during PCB fabrication makes it easy to create equipotential protection rings, preventing leakage current caused by excessive voltage differences, which could lead to excessive noise in the circuit.

[0074] The specific implementation of the microcurrent generating circuit in the above embodiments has been described in detail in the embodiments related to the method, and will not be elaborated here.

[0075] Any modifications, additions, and equivalent substitutions made within the scope of the principles of this invention shall still fall within the patent coverage of this invention.

Claims

1. A method of micro-current generation, characterized by, The method comprises the following steps: Converting the working electrode voltage in the input terminal into a working voltage with reference to a reference potential by using a high-impedance voltage follower; Connecting the input voltage to the inverting terminal of an adder and the working voltage to the non-inverting terminal of the adder to obtain an output voltage; Both the operational amplifier in the high-impedance voltage follower and the operational amplifier in the adder are double operational amplifiers; The high-impedance voltage follower comprises a first operational amplifier, a second operational amplifier, a fourth operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first compensation resistor and a second compensation resistor; The working electrode voltage in the input terminal is connected to the first end of the high-impedance voltage follower, the first end of the high-impedance voltage follower is connected to the first end of the first resistor and the first end of the fifth resistor, the second end of the first resistor is connected to the inverting terminal of the first operational amplifier and the first end of the second resistor, the second end of the second resistor is connected to the output terminal of the first operational amplifier and the first end of the third resistor, the non-inverting terminal of the first operational amplifier is connected to the first end of the first compensation resistor, the second end of the first compensation resistor is connected to the first end of the second compensation resistor, the second end of the second compensation resistor is connected to the non-inverting terminal of the second operational amplifier, the second end of the third resistor is connected to the first end of the fourth resistor and the inverting terminal of the second operational amplifier, the second end of the fifth resistor is connected to the second end of the fourth resistor, the output terminal of the second operational amplifier and the non-inverting terminal of the fourth operational amplifier, the second end of the high-impedance voltage follower is connected to the non-inverting terminal of the adder, the output terminal of the fourth operational amplifier and the inverting terminal of the adder; The output voltage and the working electrode voltage are connected to the two ends of a standard conversion resistor to obtain an output micro-current.

2. The micro-current generation method of claim 1, wherein, The resistance values of the first resistor, the second resistor, the third resistor and the fifth resistor are the same, and the resistance value of the fourth resistor is twice that of the first resistor.

3. The micro-current generation method of claim 1, wherein, The adder comprises: a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a third operational amplifier; The second end of the high-impedance voltage follower is connected to the non-inverting terminal of the adder, the non-inverting terminal of the adder is connected to the first end of the eighth resistor, the second end of the eighth resistor is connected to the first end of the ninth resistor and the non-inverting terminal of the third operational amplifier, the inverting terminal of the third operational amplifier is connected to the first end of the seventh resistor and the second end of the sixth resistor, the first end of the sixth resistor is connected to the output terminal of the third operational amplifier and the output terminal of the adder, and the second end of the seventh resistor is connected to the inverting terminal of the adder.

4. The micro-current generating method of claim 3, wherein, The resistance values of the seventh resistor and the eighth resistor are equal, the resistance values of the sixth resistor and the ninth resistor are equal, and the resistance value of the seventh resistor is twice that of the sixth resistor.

5. The method of claim 1 to 4, wherein The input voltage is a specific voltage value output by a digital-to-analog conversion device.

6. A micro-current generating circuit, characterized by, The method comprises: an adder, a high-impedance voltage follower and a standard conversion resistor; The working electrode voltage in the input terminal is connected to the first end of the high-impedance voltage follower and the first end of the standard conversion resistor, the second end of the high-impedance voltage follower is connected to the non-inverting terminal of the adder, the input voltage is connected to the inverting terminal of the adder, and the output terminal of the adder is connected to the second end of the standard conversion resistor; The high-impedance voltage follower comprises a first operational amplifier, a second operational amplifier, a fourth operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first compensation resistor and a second compensation resistor; the working electrode voltage in the input terminal is connected to the first end of the high-impedance voltage follower, the first end of the high-impedance voltage follower is connected with the first end of the first resistor and the first end of the fifth resistor respectively, the second end of the first resistor is connected with the inverting terminal of the first operational amplifier and the first end of the second resistor respectively, the second end of the second resistor is connected with the output terminal of the first operational amplifier and the first end of the third resistor respectively, the non-inverting terminal of the first operational amplifier is connected with the first end of the first compensation resistor, the second end of the first compensation resistor is connected with the first end of the second compensation resistor, the second end of the second compensation resistor is connected with the non-inverting terminal of the second operational amplifier, the second end of the third resistor is connected with the first end of the fourth resistor and the inverting terminal of the second operational amplifier respectively, the second end of the fifth resistor is connected with the second end of the fourth resistor, the output terminal of the second operational amplifier and the non-inverting terminal of the fourth operational amplifier respectively, the second end of the high-impedance voltage follower is connected with the non-inverting terminal of the adder, the output terminal of the fourth operational amplifier and the inverting terminal respectively; The adder comprises a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a third operational amplifier; the second end of the high-impedance voltage follower is connected with the non-inverting terminal of the adder, the non-inverting terminal of the adder is connected with the first end of the eighth resistor, the second end of the eighth resistor is connected with the first end of the ninth resistor and the non-inverting terminal of the third operational amplifier respectively, the inverting terminal of the third operational amplifier is connected with the first end of the seventh resistor and the second end of the sixth resistor respectively, the first end of the sixth resistor is connected with the output terminal of the third operational amplifier and the output terminal of the adder respectively, the second end of the seventh resistor is connected with the inverting terminal of the adder.

7. The micro-current generating circuit of claim 6, wherein, The resistance values of the first resistor, the second resistor, the third resistor and the fifth resistor are the same, the resistance value of the fourth resistor is twice that of the first resistor; the resistance values of the seventh resistor and the eighth resistor are equal, the resistance values of the sixth resistor and the ninth resistor are equal, and the resistance value of the seventh resistor is twice that of the sixth resistor.

8. The micro-current generating circuit of claim 6 or 7, wherein, The first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier are all double operational amplifiers.

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