High-precision current mirror image circuit for industrial Internet of Things service

Abstract

The invention discloses a high-precision current mirror circuit for industrial Internet of Things service, which comprises a reference branch, an operational amplifier, a bias branch and a current source branch, and is characterized in that the current source branch comprises a current source MOS (Metal Oxide Semiconductor) tube and a working circuit; the output end of the operational amplifier is simultaneously connected with the grid electrode of the reference current source MOS tube, the grid electrode of the bias MOS tube and the grid electrode of the current source MOS tube, the structure of the reference working circuit is the same as that of the working circuit, and the size of the reference working circuit is 1 / N of that of the working circuit. The reference working circuit in the reference branch circuit is used for scaling the working circuit in the current source branch circuit at equal proportion, and meanwhile, operational amplifier feedback is introduced, so that the drain terminal voltage of the bias MOS tube is equal to that of the current source MOS tube, the influence of the channel length modulation effect on the current mirror image precision is eliminated, the output current of the current mirror has no error, and the current mirror image precision is improved. And a high-precision bias current source can be provided for analog and radio frequency circuits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial internet of things service, and particularly relates to a high-precision current mirror circuit for industrial internet of things service. BACKGROUND

[0002] The current mirror is a commonly used circuit structure in analog and radio frequency integrated circuits, and is used for copying a reference current to provide an accurate bias current source for a working circuit, so that the circuit works at a proper DC bias point and ensures normal work of the circuit.

[0003] The current mirror circuit is required in many single-ended, differential and pseudo-differential circuit structures, and the current mirror should not be affected by temperature, power supply and process, and should output a stable and accurate bias current without consuming too much voltage margin. The traditional current mirror circuit as shown in FIG. 1 is basically designed to copy a reference current I ref ’ to obtain a current source I out ’. Figure 1 In the current mirror circuit, M1’ is biased by I ref ’, and generates a gate-source voltage V X ’ that is uniquely determined by I ref ’. X The V X ’ is added between the gate and source of M2’, and then M2’ outputs I out ’ = I ref ’. Ignoring the channel length modulation effect, it can be known that the same transistors working in the saturation region and having equal gate-source voltages transmit the same current. In order to reduce the error caused by the edge diffusion of the source and drain, M1’ and M2’ usually have the same gate length, and if the gate width of M2’ is proportional to the gate width of M1’, an output current of any size can be obtained through the current mirror circuit: Figure 1

[0004] (1).

[0005] Wherein, W ’ is the gate width of M2’, and W ’ is the gate width of M1’.

[0006] As can be seen from expression (1), the output current I out ’ can accurately copy the bias current without being affected by the process and temperature.

[0007] However, the above analysis ignores the channel length modulation effect. Under the condition of modern CMOS process, the channel length of MOS is gradually reduced according to Moore's law, and the minimum channel length has reached the level of 10 nm or less, and the channel length modulation effect is more and more significant, which causes great error in the output current of the current mirror. SUMMARY

[0008] The application aims to provide a high-precision current mirror circuit for industrial internet of things services, which uses a reference working circuit in a reference branch to proportionally scale a working circuit in a current source branch, simultaneously introduces an operational amplifier feedback, and makes the drain voltage of a bias MOS tube equal to that of a current source MOS tube, so as to eliminate the influence of channel length modulation effect on the current mirror precision, make the output current of the current mirror without error, and provide a high-precision bias current source for analog and radio frequency circuits.

[0009] To achieve the above object, the application provides the following technical scheme: a high-precision current mirror circuit for industrial internet of things services, comprising a reference branch, an operational amplifier, a bias branch and a current source branch, the current source branch comprises a current source MOS tube and a working circuit, the drain of the current source MOS tube is connected with the working circuit, the bias branch comprises a bias MOS tube and a reference current, the drain of the bias MOS tube is connected with the reference current, the gate of the bias MOS tube is connected with the gate of the current source MOS tube, the reference branch comprises a reference current source MOS tube and a reference working circuit, the drain of the reference current source MOS tube is connected with the reference working circuit and the negative input of the operational amplifier, the output of the operational amplifier is connected with the gate of the reference current source MOS tube, the gate of the bias MOS tube and the gate of the current source MOS tube, the structure of the reference working circuit is the same as that of the working circuit, and the size of the reference working circuit is 1 / N of the size of the working circuit.

[0010] Further preferably, a capacitor is connected between the positive input of the operational amplifier and the output thereof.

[0011] Further preferably, the gate length of the bias MOS tube, the current source MOS tube and the reference current source MOS tube is equal.

[0012] Further preferably, the reference current I ref The formula of the current source I out is as follows: (2); wherein, V Y is the gate-source voltage of the current source MOS tube, V X is the gate-source voltage of the bias MOS tube, is the gate width of the current source MOS tube, is the gate width of the bias MOS tube, and λ is the channel length modulation coefficient.

[0013] Further preferably, the working circuit comprises a thick gate tube, and the source of the thick gate tube is connected with the drain of the current source MOS tube.

[0014] Further preferably, the reference working circuit comprises a reference thick gate tube, and the source of the reference thick gate tube is connected with the negative input of the operational amplifier.

[0015] Further preferably, the gate of the thick-gate transistor is connected to the gate of the reference thick-gate transistor.

[0016] Further preferably, an inductor is further included, and the inductor is connected to the drain of the thick-gate transistor.

[0017] Further preferably, the thick-gate transistor and the reference thick-gate transistor form a common-source common-gate structure.

[0018] Further preferably, the reference current is an adjustable reference current.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. The present application uses the reference working circuit in the reference branch to scale the working circuit in the current source branch in proportion, and introduces an operational amplifier feedback, so that the drain voltages of the bias MOS transistor and the current source MOS transistor are equal, thereby eliminating the influence of the channel length modulation effect on the current mirror precision, and making the output current of the current mirror without error, which can provide a high-precision bias current source for analog and radio frequency circuits.

[0021] 2. In order to suppress the influence of the channel length modulation, the general method is to increase the channel length to reduce the channel length modulation coefficient λ, but the characteristic frequency of the MOS is reduced, which is not suitable for radio frequency circuits. The present application adds a reference branch (reference current source MOS transistor, reference working circuit), an operational amplifier, and a working circuit of the current source branch, and makes the reference working circuit scaled by 1 / N of the working circuit in proportion, so that the direct current voltage values of the corresponding nodes of the reference working circuit and the working circuit are equal. The feedback loop formed by the operational amplifier makes the direct current voltage values of the positive input terminal and the negative input terminal of the operational amplifier equal, and finally makes the drain voltages of the bias MOS transistor and the current source MOS transistor equal, thereby eliminating the influence of the channel length modulation effect on the current mirror precision. The high-precision current mirror circuit proposed in the present application will not cause the increase of the gate capacitance or occupy too much voltage margin.

[0022] 3. The current mirror proposed in the present application is a static circuit, and the gain and bandwidth of the operational amplifier are not too strict, so the operational amplifier will not consume too much area and power consumption.

[0023] 4. The high-precision current mirror circuit proposed in the present application has the working circuit size being a multiple of the reference working circuit S size, and K and N are independent design variables. When the reference current I changes, the accuracy of the mirror is not affected. ref

[0024] 5. In order to ensure the loop stability, the operational amplifier is connected with a capacitor between the positive input terminal and the output terminal. ​

[0025] 6. The application can be extended to other analog, RF integrated circuit technology areas that include current mirrors.

[0026] 7. The current source MOS transistor M2 in the current source branch of the embodiment 2 of the application determines the operating current of the power amplifier and forms a common source and common gate structure with the thick gate transistor M4 that functions as high voltage protection, the reference operating circuit S includes a reference thick gate transistor M5, the source of the reference thick gate transistor M5 is connected with the negative input terminal of the operational amplifier; the gate of the thick gate transistor M4 is connected with the gate of the reference thick gate transistor M5, this structure forms a common source and common gate RF power amplifier that includes a high precision current mirror circuit, and the size of the reference thick gate transistor M5 is N times of the thick gate transistor M4, these structures are different from the common source and common gate current source structure, and can solve the problem that it is very difficult to ensure that the drain voltages of the bias MOS transistor and the current source MOS transistor are consistent under different process angles and different temperatures.

[0027] 8. In order to solve the influence of the channel modulation effect, the prior art increases a transistor on the current source MOS transistor M2, adjusts the gate voltage Vb of the transistor on the top, affects the voltage at the point Y, so that the voltages at the points X and Y are equal, but this method increases a transistor, that is, an additional voltage consumption is needed, so that the battery consumption is increased and the battery efficiency is reduced. The application avoids this problem, and specifically, the gate of the thick gate transistor in the embodiment 2 of the application is connected with the gate of the reference thick gate transistor, which can solve the problem that the gate-source voltage V Y In addition to the need for an overdrive voltage, an additional threshold voltage is also needed, so that the power supply voltage of the circuit does not need to be increased by a threshold voltage level, the battery efficiency can be avoided to be reduced, and the use time of the battery is greatly saved.

[0028] 9. The current source MOS transistor M2 of the application should take the minimum gate length to provide the maximum transconductance, but the minimum gate length means that the channel length modulation effect will be very obvious, and at the same time, in order to make the output power and gain of the power amplifier not be affected by the power supply, temperature and process fluctuation, the reference current I ref is designed to be adjustable within a certain range to adjust the operating current of the power amplifier.

[0029] Additional aspects and advantages of the application will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a basic current mirror circuit;

[0031] Figure 2 is a common source and common gate current mirror circuit;

[0032] Figure 3A high-precision current mirror circuit structure schematic diagram provided by the present application;

[0033] Figure 4 A schematic diagram of the embodiment 2 of the present application.

[0034] Wherein, M1, bias MOS tube; M2, current source MOS tube; M3, reference current source MOS tube; M4, thick gate tube; M5, reference thick gate tube; I ref , reference current; C, capacitor; L1, inductor; S, reference working circuit. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0036] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium, or can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0037] Embodiment 1

[0038] In order to solve the above problems, the present application provides a technical solution: a high-precision current mirror circuit for industrial internet of things service, as Figures 1-4 shown, comprising a reference branch, an operational amplifier, a bias branch, a current source branch, the current source branch comprising a current source MOS tube M2, a working circuit, wherein the current source MOS tube M2 works in the saturation region; the drain of the current source MOS tube M2 is connected with the working circuit, and the current source MOS tube M2 directly determines the direct current working point of the working circuit, the bias branch comprising a bias MOS tube M1, a reference current I ref , the gate of the bias MOS tube M1 is connected with the gate of the current source MOS tube M2, so that the bias MOS tube M1 can provide the gate bias for the current source MOS tube M2; the drain of the bias MOS tube M1 is connected with the reference current I refThe connection, reference branch includes reference current source MOS transistor M3, reference working circuit S, the drain of reference current source MOS transistor M3 is connected with reference working circuit S and the negative input terminal of operational amplifier simultaneously, the output terminal of operational amplifier is connected with the gate of reference current source MOS transistor M3, the gate of biasing MOS transistor M1 and the gate of current source MOS transistor M2 simultaneously, the source of reference current source MOS transistor M3, the source of biasing MOS transistor M1 and the source of current source MOS transistor M2 are grounded, the DC working point of reference working circuit S is determined by reference current source MOS transistor M3, the structure of reference working circuit S is same with working circuit, and the size of reference working circuit S is N / 1 of working circuit size.

[0039] Working principle: the present application considers limited drain end output impedance, introduces channel length modulation coefficient λ, and the formula of current source I ref is obtained by copying reference current I out .

[0040] (2) ;

[0041] Wherein V Y is the gate-source voltage of current source MOS transistor M2, V X is the gate-source voltage of biasing MOS transistor M1, is the gate width of current source MOS transistor M2, is the gate width of biasing MOS transistor M1.

[0042] V Y in expression (2) is influenced by the biasing branch, and can not be equal to V X , so that I out may deviate from the design value greatly, and it is difficult to provide accurate current bias, thereby influencing the working state of the biasing circuit.

[0043] Further, to avoid that the working state of the circuit is influenced by power supply, temperature and process fluctuation, the present application designs reference current I ref to be adjustable within a certain range, but this can increase the difference between V Y and V X , and further deteriorate the accuracy of mirror current.

[0044] Therefore, to suppress the influence of channel length modulation, the present application increases the channel length to reduce channel length modulation coefficient λ, and according to expression (2), under the same difference between V Y and V X , smaller λ can obtain more accurate current source I outHowever, this method reduces the characteristic frequency of the MOS, and is not suitable for radio frequency circuit: on the one hand, the increase of the channel length will reduce the transconductance provided by the MOS per unit gate width, and the radio frequency amplifier cannot take full advantage of the process; on the other hand, under the premise that the gate bias and the output current are the same, the increase of the gate length L will inevitably require the gate width W to change in proportion, which will result in a larger layout area, and at the same time, the MOS gate capacitance will increase approximately in square rate, which will seriously deteriorate the load of the previous stage circuit.

[0045] Therefore, the present application adds a reference branch (reference current source MOS M3, reference working circuit S), an operational amplifier, and a working circuit of the current source branch, as shown in the formula (1). Figure 3

[0046] Since the reference working circuit S is scaled by 1 / N of the working circuit, the direct current voltage values of the corresponding nodes of the reference working circuit S and the working circuit are equal, that is, V Y =V Z , wherein V Y is the gate-source voltage of the current source MOS M2, V Z is the gate-source voltage of the reference current source MOS M3, and the feedback loop formed by the operational amplifier makes the direct current voltage values of the positive input terminal and the negative input terminal of the operational amplifier equal, that is, V X =V Z , so that finally V X =V Y , and according to the expression (2), the influence of the channel length modulation coefficient λ can be completely eliminated, and the current source MOS M2 can accurately output the mirror current (that is, the current source I ref ) of the reference current I out , to provide an accurate current bias for the working circuit.

[0047] (3);

[0048] wherein K is a design variable, and N is the multiple of the size of the working circuit relative to the size of the reference working circuit S.

[0049] According to the formula (3), the high-precision current mirror circuit proposed by the present application will not cause the increase of the gate capacitance or the occupation of too much voltage margin. At the same time, the current mirror proposed by the present application is a static circuit, and the gain and bandwidth of the operational amplifier are not too strict, so the operational amplifier will not consume too much area and power consumption.

[0050] In addition, the high-precision current mirror circuit proposed by the present application, since N and K are independent design variables, when the reference current I ref changes, the accuracy of the mirror will not be affected.

[0051] ​In order to ensure the loop stability, a capacitor C is connected between the positive input terminal of the operational amplifier and the output terminal of the operational amplifier, and the capacitor C is a compensation capacitor.

[0052] Embodiment 2

[0053] The common-source common-gate current source structure as shown in Figure 2 can also suppress the channel length modulation effect. The common-source common-gate current source structure is a connection structure of the drain of the current source MOS transistor M2''' and the source of the MOS transistor P, and by selecting a proper V b (V b as the gate-source voltage of the MOS transistor P), V Y =V X , and the high output impedance of the common-source common-gate structure makes V Y to a certain extent immune to the change of the output terminal voltage V P , controls the difference between V Y and V X within an acceptable range, and obtains a more accurate I out . However, the problem of this structure is that: first, it is difficult to ensure that V Y and V X can be accurately consistent at different process angles and different temperatures; second, the minimum voltage allowed at the current output terminal V P is two overdrive voltages plus a threshold voltage, which occupies more voltage margin compared with the case that V Y only needs an overdrive voltage, so that the power supply voltage of the circuit needs to be increased by a threshold voltage level, which causes the battery efficiency to be reduced and greatly shortens the battery usage time.

[0054] The specific principle of solving the above problems of the present application is that, as shown in Figure 2 , the X point and the gate end of the biasing MOS transistor M1 are connected together, so the voltage of the X point is equal to the threshold voltage of the biasing MOS transistor M1 + an overdrive voltage. The voltages of the X point and the Y point are both large. The principle of embodiment 2 is as shown in Figure 3 and Figure 4 , the voltages of the Z point and the X point are not connected to the gate end, so they do not need to be equal to the threshold voltage + the overdrive voltage, and can be designed to be smaller, so that the voltage of the Y point can also be smaller, thereby solving the problem of voltage utilization rate of the working branch.

[0055] Based on this, the application provides embodiment 2, which is different from embodiment 1 in that the working circuit comprises a thick gate tube M4, the source of the thick gate tube M4 is connected with the drain of the current source MOS tube M2. The reference working circuit S comprises a reference thick gate tube M5, the source of the reference thick gate tube M5 is connected with the negative input end of the operational amplifier; the gate of the thick gate tube M4 is connected with the gate of the reference thick gate tube M5, which constitutes the common source and common gate radio frequency power amplifier comprising the high-precision current mirror circuit. And the thick gate tube M4 and the reference thick gate tube M5 constitute the common source and common gate structure; further comprising an inductor L1, the inductor L1 is connected with the drain of the thick gate tube M4.

[0056] The current source MOS tube M2 in the current source branch determines the working current of the power amplifier and constitutes the common source and common gate structure with the thick gate tube M4 which plays a high voltage protection role, the inductor L is a load, the sizes of the devices in the reference branch are N / 1 of the working branch, since the inductor L has no effect on the DC circuit, to save the area, the reference branch does not need to contain the inductor scaled by the same proportion. The size of the biasing MOS tube M1 is N times of the reference current source MOS tube M3 to ensure the stability of the loop, it is necessary to point out that N is preferably 2, but the value of N can also be adjusted according to actual needs, other values can be taken, the above values are not intended to limit the value range of N, but to better illustrate the principle.

[0057] In the common source and common gate radio frequency power amplifier, the current source MOS tube M2 should take the minimum gate length to provide the maximum transconductance, but the minimum gate length means that the channel length modulation effect will be very obvious, at the same time, to make the output power and the gain of the power amplifier not be affected by the power supply, temperature and process fluctuation, the reference current I ref is designed to be adjustable within a certain range to adjust the working current of the power amplifier, if the reference current I Figure 1 is not adjustable, the gate-source voltage and the drain-source voltage of the current source MOS tube M2 will change when the reference current I ref changes, it is difficult to ensure that the working current of the power amplifier can keep the accurate proportion with the reference current I ref . In this embodiment 2, the equal proportion scaling of the reference working circuit and the working circuit and the feedback loop formed by the operational amplifier, the biasing MOS tube M1 and the reference current source MOS tube M3 ensure that V X is equal to V Y , within the adjustable range of the reference current I ref , the output current I D2 of the current source MOS tube M2 is always the accurate mirror of the reference current I ref , the value of I D2 is only related to N and the reference current I ref , that is:

[0058] (4);

[0059] And the power amplifier can work in the accurate current bias state.

[0060] In the description of the present application, it is to be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0061] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-precision current mirror circuit for industrial Internet of Things (IIoT) services, characterized in that, The circuit includes a reference branch, an operational amplifier, a bias branch, and a current source branch. The current source branch includes a current source MOSFET (M2) and a working circuit. The drain of the current source MOSFET (M2) is connected to the working circuit. The bias branch includes a bias MOSFET (M1) and a reference current (I). ref The drain of the bias MOSFET (M1) and the reference current (I) ref The bias MOSFET (M1) is connected to the gate of the current source MOSFET (M2). The reference branch includes a reference current source MOSFET (M3) and a reference working circuit. The drain of the reference current source MOSFET (M3) is connected to both the reference working circuit and the negative input terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the gate of the reference current source MOSFET (M3), the gate of the bias MOSFET (M1), and the gate of the current source MOSFET (M2). The structure of the reference working circuit is the same as that of the working circuit, and the size of the reference working circuit is 1 / N of the size of the working circuit.

2. The high-precision current mirror circuit for industrial IoT services according to claim 1, characterized in that: A capacitor (C) is connected between the positive input terminal and the output terminal of the operational amplifier.

3. The high-precision current mirror circuit for industrial IoT services according to claim 1, characterized in that: The gate lengths of the bias MOSFET (M1), current source MOSFET (M2), and reference current source MOSFET (M3) are equal.

4. The high-precision current mirror circuit for industrial IoT services according to claim 1, characterized in that: Reference current (I) ref The current source (I) is obtained by copying the original. out The formula for ) is; ; Among them, V Y V is the gate-source voltage of the current-source MOSFET (M2). X This is the gate-source voltage of the bias MOSFET (M1). The gate width of the current source MOSFET (M2) λ is the gate width of the biased MOSFET (M1), and λ is the channel length modulation coefficient.

5. The high-precision current mirror circuit for industrial IoT services according to claim 1, characterized in that: The operating circuit includes a thick gate transistor (M4), the source of which is connected to the drain of a current source MOSFET (M2).

6. The high-precision current mirror circuit for industrial IoT services according to claim 5, characterized in that: The reference operating circuit includes a reference thick gate transistor (M5), the source of which is connected to the negative input terminal of the operational amplifier.

7. The high-precision current mirror circuit for industrial IoT services according to claim 6, characterized in that: The gate of the thick gate transistor (M4) is connected to the gate of the reference thick gate transistor (M5).

8. The high-precision current mirror circuit for industrial IoT services according to claim 5, characterized in that: It also includes an inductor (L1) connected to the drain of the thick gate transistor (M4).

9. The high-precision current mirror circuit for industrial IoT services according to claim 7, characterized in that: The thick gate tube (M4) and the reference thick gate tube (M5) constitute a common source and common gate structure.

10. The high-precision current mirror circuit for industrial IoT services according to claim 1, characterized in that: The reference current (I) ref () is an adjustable reference current.

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