Nanoampere-level reference current source

Abstract

The invention provides a nanoampere-level reference current source, and the source comprises a voltage generation module which comprises five voltage transistors working in a sub-threshold region and a voltage transistor working in a linear region, so as to generate nanoampere-level reference current through the bulk effect of the transistors; and the reference current generation module is used for copying and outputting the nanoampere-level reference current. The voltage generation module is composed of transistors, so that the circuit structure is simple, and the circuit area and power consumption are reduced; by utilizing the bulk effect of the transistor, the resistance of the voltage generation module can be increased on the premise that the voltage of the voltage generation module is not obviously changed, and meanwhile, temperature compensation is performed on the transistor working in a sub-threshold region, so that stable nanoampere-level current is generated; therefore, the high-stability nanoampere-level current can be output by using the reference current generation module, and the problem of how to provide the high-stability nanoampere-level reference current while the circuit area and the power consumption are small is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor integrated circuit design, and in particular to a nanoampere-level reference current source. Background Art

[0002] Reference current sources are widely used in analog / mixed signal integrated circuits, and the reference current they output is the current reference for other circuit modules. Given the special role of the reference current source, if the reference current it outputs is inaccurate or unstable, it will cause abnormal operation of the subsequent circuit module. Therefore, it is necessary to ensure that the reference current output by the reference current source is almost independent of the power supply voltage and temperature. In addition, the reference current source needs to meet the requirements of low voltage, low cost, and low power consumption. Therefore, designing a reference current source with a low temperature coefficient, low process dependence, and independence from the power supply voltage becomes the key in circuit design.

[0003] In the existing reference current source circuit, the most commonly used reference current generation method is based on a bandgap reference voltage source, and resistors are added at both ends of the reference voltage to generate the reference current. However, the existing reference current generation method has the following problems: 1. The voltage of the traditional bandgap reference voltage source is relatively high, so the reference voltage source circuit is difficult to apply to low power supply voltage scenarios; 2. The reference current generated by the traditional bandgap reference voltage source is generally in the microampere level. If a lower nanoampere reference current is required, the resistance at both ends of the reference voltage source needs to be increased. However, due to the very limited area of ​​the silicon substrate, it is unrealistic to use a very large resistor to achieve a small current at the nanoampere level. If an external high-precision reference resistor is used, it will not only increase the cost, but also lead to a decrease in the integration of transistors. 3. The traditional bandgap reference technology has been developed for many years, and its circuit structure has been basically fixed, making it difficult to change and innovate. In addition, its circuit area is large and its power consumption is high. Summary of the invention

[0004] The object of the present invention is to provide a nanoampere reference current source to solve the problem of how to provide a nanoampere reference current with high stability while reducing the circuit area and power consumption.

[0005] In order to solve the above technical problems, the present invention provides a nanoampere level reference current source, comprising: A voltage generating module, comprising a first voltage transistor, a second voltage transistor, a third voltage transistor, a fourth voltage transistor and a fifth voltage transistor all working in a subthreshold region and a sixth voltage transistor working in a linear region, so as to generate a nanoampere-level reference current by utilizing the body effect of the first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor, and output the current through the sixth voltage transistor; The reference current generating module is used to copy and output the nanoampere-level reference current.

[0006] Optionally, in the nanoampere-level reference current source, the drain of the first voltage transistor is connected to the gate, and the gate is connected to the gate of the second voltage transistor and the gate of the third voltage transistor, and the source is connected to the drain of the second voltage transistor; the source of the second voltage transistor is connected to the drain of the third voltage transistor; the source of the third voltage transistor is connected to a power supply; the drain of the fourth voltage transistor is connected to the gate, and the source is connected to the drain of the third voltage transistor, and the gate outputs a first voltage; the drain of the first voltage transistor and the drain of the fourth voltage transistor are connected to the reference current generating module; the gate of the fifth voltage transistor is connected to the gate of the fourth voltage transistor, the source is connected to the drain of the sixth voltage transistor, and the drain is connected to the reference current generating module; the source of the sixth voltage transistor is connected to the power supply, and the gate is connected to the reference current generating module; the gate-source voltage of the fifth voltage transistor is a second voltage.

[0007] Optionally, in the nanoampere-level reference current source, the substrate potentials of the first voltage transistor, the second voltage transistor and the third voltage transistor are all 0, and the source terminal voltages of the first voltage transistor, the second voltage transistor and the third voltage transistor are all different.

[0008] Optionally, in the nanoampere-level reference current source, the sizes of the first voltage transistor, the second voltage transistor and the third voltage transistor are adjusted to adjust the magnitude of the first voltage.

[0009] Optionally, in the nanoampere-level reference current source, the sizes of the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor are adjusted to adjust the temperature coefficient of the drain current of the sixth voltage transistor; the size of the sixth voltage transistor is adjusted to adjust the size of the drain current of the sixth voltage transistor.

[0010] Optionally, in the nanoampere-level reference current source, the reference current generating module includes a current mirror circuit, and the current mirror circuit is used to convert the drain current of the sixth voltage transistor according to a preset ratio to output a reference current.

[0011] Optionally, in the nanoampere-level reference current source, the current mirror circuit includes a first current transistor, a second current transistor, a third current transistor, a fourth current transistor, a fifth current transistor, a sixth current transistor, a seventh current transistor and an eighth current transistor; The source of the first current transistor, the source of the third current transistor, the source of the fifth current transistor and the source of the seventh current transistor are connected to a power supply; the gate of the first current transistor, the gate of the third current transistor, the gate of the fifth current transistor and the gate of the seventh current transistor are connected; the gate of the second current transistor, the gate of the fourth current transistor, the gate of the sixth current transistor and the gate of the eighth current transistor are connected; the source of the second current transistor is connected to the drain of the first current transistor, and the drain outputs a reference current; the source of the fourth current transistor is connected to the drain of the third current transistor, and the drain is connected to the drain of the first voltage transistor; the source of the sixth transistor is connected to the drain of the fifth current transistor, and the drain is connected to the drain of the fourth voltage transistor; the source of the eighth current transistor is connected to the drain of the seventh current transistor, and the drain is connected to the drain of the fifth voltage transistor; the gate and drain of the seventh current transistor are connected, and the gate and drain of the eighth current transistor are connected; the source of the eighth current transistor is connected to the gate of the sixth voltage transistor.

[0012] Optionally, in the nanoampere-level reference current source, the first current transistor, the second current transistor, the third current transistor, the fourth current transistor, the fifth current transistor, the sixth current transistor, the seventh current transistor and the eighth current transistor all operate in the subthreshold region.

[0013] Optionally, in the nanoampere-level reference current source, the first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor, the fifth voltage transistor and the sixth voltage transistor are all NMOS; the first current transistor, the second current transistor, the third current transistor, the fourth current transistor, the fifth current transistor, the sixth current transistor, the seventh current transistor and the eighth current transistor are all PMOS.

[0014] The nano-ampere level reference current source provided by the present invention comprises: a voltage generating module, comprising a first voltage transistor, a second voltage transistor, a third voltage transistor, a fourth voltage transistor and a fifth voltage transistor all working in a subthreshold region and a sixth voltage transistor working in a linear region, so as to generate a nano-ampere level reference current by utilizing the body effect of the first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor, and output it through the sixth voltage transistor; a reference current generating module, used for replicating and outputting the nano-ampere level reference current obtained by making a difference between the first voltage and the second voltage. Since the voltage generating module is composed of transistors, the circuit structure is simple, and the circuit area and power consumption are reduced; by utilizing the transistor body effect, the resistance of the voltage generating module can be increased without significantly changing the voltage of the voltage generating module, and the transistor working in the subthreshold region is temperature compensated, thereby generating a stable nano-ampere level current, and then the reference current generating module can be used to output a nano-ampere level current with high stability, solving the problem of how to provide a nano-ampere level reference current with high stability while reducing the circuit area and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A block diagram of the nanoampere-level reference current source provided in this embodiment; Figure 2 A specific structural block diagram of the nanoampere-level reference current source provided in this embodiment; Figure 3 A circuit schematic diagram of the nanoampere-level reference current source provided in this embodiment. DETAILED DESCRIPTION

[0016] The nanoampere-level reference current source proposed in the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the accompanying drawings is often part of the actual structure. In particular, the emphasis that each drawing needs to show is different, and sometimes different proportions are used.

[0017] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of the present invention are used to distinguish similar objects in order to describe the embodiments of the present invention, rather than to describe a specific order or sequence. It should be understood that the structures used in this way can be interchanged under appropriate circumstances. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0018] According to Ohm's law, when the voltage remains constant, a very large resistor is required to generate a nanoampere current. However, in the field of integrated circuits, it is difficult to provide a large resistor due to the limited chip area. Therefore, the high impedance characteristic of transistors in the subthreshold region is usually used to generate nanoampere current.

[0019] At the same time, it is also necessary to perform temperature compensation on transistors working in the subthreshold region. Currently, the methods for temperature compensation include: ① using transistors with high and low threshold voltages in the process for temperature compensation; ② temperature compensation based on the mobility of PMOS and NMOS; ③ temperature compensation based on the gate-source voltage V of transistors in the subthreshold region. GS Perform temperature compensation.

[0020] Taking MOS (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET) as an example, a MOS working in the subthreshold region has a V GS It can usually be regarded as a voltage with a positive temperature coefficient and a voltage with a negative temperature coefficient superimposed, but the superposition of the two results in V GS Overall, it is negatively correlated with temperature (the negative correlation is large) and is not easy to compensate.

[0021] For two identical MOSs operating in the subthreshold region, V GS Make the difference and get ΔV GS , and its expression with temperature can be simplified as:

[0022] Among them, V THZ With V TZ Both are considered as positive constants that are independent of temperature. m1 and m2 are functions of temperature. The derivative of m1 with respect to temperature is approximately 0, and the derivative of m2 with respect to temperature is greater than 0, so that the superposition of the two ΔV GS It is positively correlated with temperature (the positive correlation is small), and m2 is easy to adjust.

[0023] MOS threshold voltage V TH The relationship with temperature is:

[0024] Among them, k1 and k2 are negative coefficients, V TH0 is the threshold voltage at temperature T0, T0 is the reference temperature, and T is the absolute temperature.

[0025] By using the body effect of the transistor, the transistor threshold voltage V TH The temperature coefficient of m1 is adjusted to be slightly less than 0 when it is derived with respect to temperature, so that a lower temperature coefficient can be obtained after superposition with m2.

[0026] Based on this, this embodiment provides a nanoampere level reference current source, such as Figure 1 As shown, including: A voltage generating module, comprising a first voltage transistor, a second voltage transistor, a third voltage transistor, a fourth voltage transistor and a fifth voltage transistor all working in a subthreshold region and a sixth voltage transistor working in a linear region, so as to generate a nanoampere-level reference current by utilizing the body effect of the first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor, and output the current through the sixth voltage transistor; The reference current generating module is used to copy and output the nanoampere-level reference current.

[0027] The nanoampere-level reference current source provided in this embodiment has a simple circuit structure, and the circuit area and power consumption are reduced because the voltage generating module is composed of transistors. By utilizing the transistor body effect, the resistance of the voltage generating module can be increased without significantly changing the voltage of the voltage generating module, and temperature compensation is performed on the transistors working in the subthreshold region, thereby generating a stable nanoampere-level current. The reference current generating module can then be used to output a nanoampere-level current with high stability, thereby solving the problem of how to provide a highly stable nanoampere-level reference current while reducing the circuit area and power consumption.

[0028] Specifically, in this embodiment, Figure 2 As shown, the voltage generating module includes a first voltage generating unit and a second voltage generating unit, wherein the first voltage generating module only includes a first voltage transistor NM1, a second voltage transistor NM2, a third voltage transistor NM3 and a fourth voltage transistor NM4; the second voltage generating module only includes a fifth voltage transistor NM5 and a sixth voltage transistor NM6.

[0029] In this embodiment, if Figure 3As shown, the drain of the first voltage transistor NM1 is connected to the gate, and the gate is connected to the gate of the second voltage transistor NM2 and the gate of the third voltage transistor NM3, and the source is connected to the drain of the second voltage transistor NM2; the source of the second voltage transistor NM2 is connected to the drain of the third voltage transistor NM3; the source of the third voltage transistor NM3 is connected to the power supply VSS; the drain of the fourth voltage transistor NM4 is connected to the gate, and the source is connected to the drain of the third voltage transistor NM3, and the gate outputs the first voltage V CTAT1 ; The drain of the first voltage transistor NM1 and the drain of the fourth voltage transistor NM4 are connected to the reference current generating module.

[0030] In this embodiment, the source voltages of the first voltage transistor NM1, the second voltage transistor NM2, and the third voltage transistor NM3 are all different, but the substrate potentials of the three are the same and are all 0. TH The relationship expression with temperature, or, from the body effect, it can be known that the threshold voltage V of the first voltage transistor NM1, the second voltage transistor NM2, and the third voltage transistor NM3 TH It has different temperature coefficients, and the temperature coefficient can be adjusted by adjusting the size of the transistor, thereby achieving temperature compensation for the first voltage generating unit and ensuring the stability of the output nanoampere current.

[0031] In this embodiment, since the source of the fourth voltage transistor NM4 is connected to the drain of the third voltage transistor NM3, the gate voltage V G4 It can be expressed as:

[0032] Among them, V GS4 represents the gate-source voltage of the fourth voltage transistor NM4, V DS3 represents the drain-source voltage of the third voltage transistor NM3.

[0033] At the same time, there are , therefore, the above formula can be expressed as:

[0034] It can be seen that the gate voltage V G4 Inversely proportional to absolute temperature within a certain temperature range.

[0035] The gate voltage V of the fourth voltage transistor NM4 is G4 is the first voltage V CTAT1 , that is, V G4 =V CTAT1In this way, the body effect of the first voltage transistor NM1, the second voltage transistor NM2, the third voltage transistor NM3 and the fourth voltage transistor NM4 can be utilized to make the current at the nanoampere level without significantly changing the first voltage, and when the size of the first voltage transistor NM1, the second voltage transistor NM2 and the third voltage transistor NM3 is adjusted, the resistance value of the transistor of the adjusted size can be changed, thereby adjusting the size of the nanoampere current.

[0036] In practical applications, the first voltage transistor NM1 , the second voltage transistor NM2 , the third voltage transistor NM3 , and the fourth voltage transistor NM4 are all NMOS.

[0037] And, in this embodiment, if Figure 3 As shown, the gate of the fifth voltage transistor NM5 is connected to the gate of the fourth voltage transistor NM4, the source is connected to the drain of the sixth voltage transistor NM6, and the drain is connected to the reference current generating module; the source of the sixth voltage transistor NM6 is connected to the power supply VSS, and the gate is connected to the reference current generating module; the gate-source voltage V GS5 is the second voltage V CTAT2 .

[0038] Specifically, in this embodiment, the fifth voltage transistor NM5 operates in the subthreshold region, and the sixth voltage transistor NM6 operates in the linear region. Thus, the sixth voltage transistor NM6 can be regarded as a linear resistor, denoted as KR6. The gate voltage V G5 It can be expressed as:

[0039] Among them, V GS5 represents the gate-source voltage of the fifth voltage transistor NM5, I D6 represents the drain current of the sixth voltage transistor NM6, and KR6 represents the equivalent resistance of the sixth voltage transistor NM6.

[0040] It can be seen that the gate-source voltage V GS5 and gate voltage V G5 They are inversely proportional to the absolute temperature within a certain temperature range.

[0041] Meanwhile, in this embodiment, since the gate voltages of the fourth voltage transistor NM4 and the fifth voltage transistor NM5 are equal, that is, V G4 =V G5 Therefore, combining the above formulas, we can get:

[0042] Substituting the equation:

[0043] Still taking the MOS transistor as an example, when the drain-source voltage V DS When >0.1V, the MOS current expression working in the subthreshold region is as follows:

[0044] in, , , S i is the width-to-length ratio of the i-th MOS tube, , μ is the carrier mobility, C OX is the gate oxide capacitance per unit area, V GS is the gate-source voltage of the MOS tube, V TH is the threshold voltage of the MOS tube, q is the electron charge, η is the subthreshold slope factor, k is the Boltzmann constant, and T is the absolute temperature.

[0045] Combining the above formulas, we can get:

[0046] When the sizes of the second voltage transistor NM2, the third voltage transistor NM3, the fourth voltage transistor NM4 and the fifth voltage transistor NM5 are adjusted, the drain current I of the sixth voltage transistor NM6 can be adjusted. D6 The temperature coefficient of the drain current is thus ensured to be stable; by adjusting the size of the sixth voltage transistor NM6, the drain current I of the sixth voltage transistor NM6 can be adjusted. D6 size.

[0047] In this embodiment, if Figure 3 As shown, the drain current I D6 That is, the initial reference current of the input reference current generating module, and the initial reference current is a nanoampere level current.

[0048] In practical applications, the fifth voltage transistor NM5 and the sixth voltage transistor NM6 are both NMOS.

[0049] Furthermore, in this embodiment, the reference current generating module includes a current mirror circuit, and the current mirror circuit is used to convert the drain current I D6 Convert according to the preset ratio to output the reference current I REF .

[0050] Specifically, in this embodiment, Figure 3As shown, the current mirror circuit includes a first current transistor PM1, a second current transistor PM2, a third current transistor PM3, a fourth current transistor PM4, a fifth current transistor PM5, a sixth current transistor PM6, a seventh current transistor PM7 and an eighth current transistor PM8.

[0051] Among them, the source of the first current transistor PM1, the source of the third current transistor PM3, the source of the fifth current transistor PM5 and the source of the seventh current transistor PM7 are connected to the power supply VDD; the gate of the first current transistor PM1, the gate of the third current transistor PM3, the gate of the fifth current transistor PM5 and the gate of the seventh current transistor PM7 are connected; the gate of the second current transistor PM2, the gate of the fourth current transistor PM4, the gate of the sixth current transistor PM6 and the gate of the eighth current transistor PM8 are connected; the source of the second current transistor PM2 is connected to the drain of the first current transistor PM1, and the drain outputs the reference current I REF ; The source of the fourth current transistor PM4 is connected to the drain of the third current transistor PM3, and the drain is connected to the drain of the first voltage transistor NM1; the source of the sixth transistor PM6 is connected to the drain of the fifth current transistor PM5, and the drain is connected to the drain of the fourth voltage transistor NM4; the source of the eighth current transistor PM8 is connected to the drain of the seventh current transistor PM7, and the drain is connected to the drain of the fifth voltage transistor NM5; the gate and drain of the seventh current transistor PM7 are connected, and the gate and drain of the eighth current transistor PM8 are connected; the source of the eighth current transistor PM8 is connected to the gate of the sixth voltage transistor NM6.

[0052] Further, in this embodiment, the first current transistor PM1, the second current transistor PM2, the third current transistor PM3, the fourth current transistor PM4, the fifth current transistor PM5, the sixth current transistor PM6, the seventh current transistor PM7 and the eighth current transistor PM8 all operate in the subthreshold region.

[0053] In this way, the current mirror formed can convert the drain current I D6 Convert according to the preset ratio and reduce noise while accurately replicating the current to ensure the reference current I REF Stable output.

[0054] In this embodiment, Figure 3 The current mirror circuit shown in FIG. 1 converts the drain current I of the sixth voltage transistor NM6 into D6 The output is converted 1:1, that is, the reference current I REF For ID6 .

[0055] Of course, in practical applications, a current mirror circuit can be designed according to actual needs, so that the drain current I D6 Flexible adjustment to obtain the required reference current I REF .

[0056] In practical applications, in the current mirror circuit provided in this embodiment, the first current transistor PM1, the second current transistor PM2, the third current transistor PM3, the fourth current transistor PM4, the fifth current transistor PM5, the sixth current transistor PM6, the seventh current transistor PM7 and the eighth current transistor PM8 are all PMOS.

[0057] The nanoampere-level reference current source provided in the present embodiment is suitable for use in current sources of various integrated circuits, and can provide accurate and stable nanoampere-level current for the integrated circuits; the nanoampere-level reference current source provided in the present embodiment, since the components only include transistors (MOS), can be highly integrated to reduce the circuit area and power consumption; the nanoampere-level reference current source provided in the present embodiment can flexibly adjust the temperature coefficient by adjusting the size of the transistor, thereby making the output nanoampere-level reference current almost unaffected by temperature; the nanoampere-level reference current source provided in the present embodiment can flexibly adjust the size of the reference current by adjusting the size of the transistor, thereby being suitable for various application scenarios.

[0058] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. In addition, the different parts between the various embodiments can also be used in combination with each other, and the present invention is not limited to this.

[0059] The nano-ampere reference current source provided in this embodiment includes: a voltage generation module, including a first voltage transistor, a second voltage transistor, a third voltage transistor, a fourth voltage transistor and a fifth voltage transistor all working in the subthreshold region and a sixth voltage transistor working in the linear region, so as to generate a nano-ampere reference current by using the body effect of the first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor, and output it through the sixth voltage transistor; a reference current generation module, used to copy and output the nano-ampere reference current obtained by making a difference between the first voltage and the second voltage. Since the voltage generation module is composed of transistors, the circuit structure is simple, and the circuit area and power consumption are reduced; by using the transistor body effect, the resistance of the voltage generation module can be increased without significantly changing the voltage of the voltage generation module, and the transistor working in the subthreshold region is temperature compensated, thereby generating a stable nano-ampere current, and then the reference current generation module can be used to output a nano-ampere current with high stability, solving the problem of how to provide a nano-ampere reference current with high stability while reducing the circuit area and power consumption.

[0060] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A nanoampere level reference current source, characterized in that: include: A voltage generating module, comprising a first voltage transistor, a second voltage transistor, a third voltage transistor, a fourth voltage transistor and a fifth voltage transistor all working in a subthreshold region and a sixth voltage transistor working in a linear region, so as to generate a nanoampere-level reference current by utilizing the body effect of the first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor, and output the current through the sixth voltage transistor; The reference current generating module is used to copy and output the nanoampere-level reference current.

2. The nanoampere level reference current source according to claim 1, characterized in that: The drain of the first voltage transistor is connected to the gate, and the gate is connected to the gate of the second voltage transistor and the gate of the third voltage transistor, and the source is connected to the drain of the second voltage transistor; the source of the second voltage transistor is connected to the drain of the third voltage transistor; the source of the third voltage transistor is connected to a power supply; the drain of the fourth voltage transistor is connected to the gate, and the source is connected to the drain of the third voltage transistor, and the gate outputs a first voltage; The drain of the first voltage transistor and the drain of the fourth voltage transistor are connected to the reference current generating module; The gate of the fifth voltage transistor is connected to the gate of the fourth voltage transistor, the source is connected to the drain of the sixth voltage transistor, and the drain is connected to the reference current generating module; The source of the sixth voltage transistor is connected to the power supply, and the gate is connected to the reference current generating module; The gate-source voltage of the fifth voltage transistor is the second voltage.

3. The nanoampere level reference current source according to claim 2, characterized in that: The substrate potentials of the first voltage transistor, the second voltage transistor and the third voltage transistor are all 0, and the source terminal voltages of the first voltage transistor, the second voltage transistor and the third voltage transistor are all different.

4. The nanoampere level reference current source according to claim 2, characterized in that: The sizes of the first voltage transistor, the second voltage transistor and the third voltage transistor are adjusted to adjust the magnitude of the first voltage.

5. The nanoampere level reference current source according to claim 2, characterized in that: Adjust the sizes of the second voltage transistor, the third voltage transistor, the fourth voltage transistor and the fifth voltage transistor to adjust the temperature coefficient of the drain current of the sixth voltage transistor; adjust the size of the sixth voltage transistor to adjust the size of the drain current of the sixth voltage transistor.

6. The nanoampere level reference current source according to claim 2, characterized in that: The reference current generating module comprises a current mirror circuit, and the current mirror circuit is used for converting the drain current of the sixth voltage transistor according to a preset ratio to output a reference current.

7. The nanoampere level reference current source according to claim 6, characterized in that: The current mirror circuit includes a first current transistor, a second current transistor, a third current transistor, a fourth current transistor, a fifth current transistor, a sixth current transistor, a seventh current transistor and an eighth current transistor; The source of the first current transistor, the source of the third current transistor, the source of the fifth current transistor and the source of the seventh current transistor are connected to a power supply; The gate of the first current transistor, the gate of the third current transistor, the gate of the fifth current transistor and the gate of the seventh current transistor are connected; the gate of the second current transistor, the gate of the fourth current transistor, the gate of the sixth current transistor and the gate of the eighth current transistor are connected; the source of the second current transistor is connected to the drain of the first current transistor, and the drain outputs a reference current; The source of the fourth current transistor is connected to the drain of the third current transistor, and the drain is connected to the drain of the first voltage transistor; the source of the sixth transistor is connected to the drain of the fifth current transistor, and the drain is connected to the drain of the fourth voltage transistor; the source of the eighth current transistor is connected to the drain of the seventh current transistor, and the drain is connected to the drain of the fifth voltage transistor; the gate and drain of the seventh current transistor are connected, and the gate and drain of the eighth current transistor are connected; the source of the eighth current transistor is connected to the gate of the sixth voltage transistor.

8. The nanoampere level reference current source according to claim 7, characterized in that: The first current transistor, the second current transistor, the third current transistor, the fourth current transistor, the fifth current transistor, the sixth current transistor, the seventh current transistor and the eighth current transistor all operate in a subthreshold region.

9. The nanoampere level reference current source according to claim 7, characterized in that: The first voltage transistor, the second voltage transistor, the third voltage transistor, the fourth voltage transistor, the fifth voltage transistor and the sixth voltage transistor are all NMOS; The first current transistor, the second current transistor, the third current transistor, the fourth current transistor, the fifth current transistor, the sixth current transistor, the seventh current transistor and the eighth current transistor are all PMOS.

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