Current amplifier

Abstract

The invention discloses a current amplifier. The current amplifier comprises a current generation unit, a negative feedback unit, a control voltage generation unit and a clamping unit, the current generation unit is used for generating input current, the control voltage generation unit is used for generating a control voltage signal, the negative feedback unit is connected with a first end of the current generation unit and an output end of the clamping unit, and the negative feedback unit is used for generating a feedback voltage signal based on the input current and output current generated by the clamping unit; the first input end and the second input end of the clamping unit are connected with the control voltage generation unit and the negative feedback unit so as to clamp the control voltage signal and the feedback voltage signal. According to the invention, the exponential relationship between the input current and the output current is constructed through the negative feedback unit, so that exponential current amplification is realized. The current amplifier provided by the invention is large in adjustment range, only needs a fixed circuit area, is low in cost, and has high-precision exponential adjustment step length.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a current amplifier. Background Art

[0002] The bias current source is an indispensable module in the analog current circuit. In some application scenarios, the output current of the bias current source needs to be controlled to span multiple orders of magnitude. One implementation method is to use a current mirror in parallel to adjust the output current. This method consumes a lot of circuit area cost when the current adjustment range is large and the adjustment step size is limited. In addition, the adjustment step size must be an integer multiple of the minimum reference current.

[0003] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0004] The object of the present invention is to provide a current amplifier which can realize an exponential amplification ratio of a bias current with a fixed circuit area, thereby solving the problems of large area cost and limited current regulation step length.

[0005] In order to achieve the above object, a specific embodiment of the present invention provides a current amplifier, which includes a current generating unit, a negative feedback unit, a control voltage generating unit and a clamping unit;

[0006] The current generating unit is used to generate input current;

[0007] The control voltage generating unit is used to generate a control voltage signal;

[0008] The negative feedback unit is connected to the first end of the current generating unit and the output end of the clamping unit, and the negative feedback unit is used to generate a feedback voltage signal based on the input current and the output current generated by the clamping unit;

[0009] The first input end of the clamping unit is connected to the control voltage generating unit, and the second input end is connected to the negative feedback unit. The clamping unit is used to clamp the control voltage signal and the feedback voltage signal.

[0010] In one or more embodiments of the present invention, the negative feedback unit includes a first voltage dividing unit and a second voltage dividing unit;

[0011] A first end of the first voltage dividing unit is connected to a reference potential, a second end of the first voltage dividing unit is connected to an output end of the clamping unit, and the first voltage dividing unit is used to generate a first voltage dividing signal between the output end of the first voltage dividing unit and the second end of the first voltage dividing unit based on the output current;

[0012] The first end of the second voltage divider unit is connected to the first end of the current generating unit and the second input end of the clamping unit, the second voltage divider unit is used to generate a second voltage divider signal between the first end of the second voltage divider unit and the second end of the second voltage divider unit based on the input current, and the second end of the second voltage divider unit is connected to the output end of the first voltage divider unit to generate a feedback voltage signal at the first end of the second voltage divider unit based on the first voltage divider signal and the second voltage divider signal.

[0013] In one or more embodiments of the present invention, the first voltage divider unit includes a first error amplifier and a first transistor, the first input end of the first error amplifier is connected to the reference potential, the second input end of the first error amplifier is connected to the first end of the first transistor and the output end of the clamping unit, the output end of the first error amplifier is connected to the control end and the second end of the first transistor and serves as the output end of the first voltage divider unit, and the control end of the first transistor is connected to the second end of the second voltage divider unit.

[0014] In one or more embodiments of the present invention, the second voltage dividing unit includes a second transistor, the control end and the second end of the second transistor are connected to the output end of the first voltage dividing unit and serve as the second end of the second voltage dividing unit, and the first end of the second transistor is connected to the second input end of the clamping unit and the current generating unit and serves as the first end of the second voltage dividing unit.

[0015] In one or more embodiments of the present invention, the clamping unit includes a second error amplifier and an output tube, the first input end of the second error amplifier is connected to the control voltage generating unit to receive a control voltage signal, the second input end of the second error amplifier is connected to the negative feedback unit, the output end of the second error amplifier is connected to the control end of the output tube and generates a first control signal, the first end of the output tube is connected to a reference potential, the second end of the output tube is connected to the negative feedback unit, and the output tube is used to generate an output current based on the first control signal.

[0016] In one or more embodiments of the present invention, the current generating unit includes a first current source, a first terminal of the first current source is connected to the negative feedback unit, and a second terminal of the first current source is connected to a reference potential.

[0017] In one or more embodiments of the present invention, the control voltage generating unit includes a second current source and a resistance unit, the second current source is connected to the first end of the resistance unit and generates a control voltage signal at the first end of the resistance unit based on the current generated by the second current source, and the second end of the resistance unit is connected to the reference potential.

[0018] In one or more embodiments of the present invention, the second current source is a current source that generates a positive temperature coefficient current or a current source that generates a zero temperature drift current.

[0019] In one or more embodiments of the present invention, the resistance unit includes a plurality of first resistors connected in series, in parallel or in mixed connection and corresponding switch units, and the resistance unit controls the switch units through digital control codes to adjust the total resistance value of the resistance unit.

[0020] A specific embodiment of the present invention provides a chip, and the chip includes the current amplifier described in any one of the implementation modes.

[0021] Compared with the prior art, the current amplifier of the present invention constructs an exponential relationship between input current and output current through a negative feedback unit, thereby realizing exponential current amplification. Then, the functional relationship between the feedback voltage signal of the negative feedback unit and the control voltage signal is constructed through the clamping action of the clamping unit, eliminating the parameters related to PVT. The current amplifier of the present invention has a large adjustment range and only requires a fixed circuit area, and has a high-precision exponential adjustment step length while being low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 4 is a circuit diagram of a current amplifier in Embodiment 1 of the present invention.

[0024] Figure 2 This is a circuit diagram of a current amplifier in Embodiment 2 of the present invention.

[0025] Figure 3 This is a circuit diagram of the current amplifier in the third embodiment of the present invention.

[0026] Figure 4 This is a simulation diagram of the relationship between the digital control code and the output current in the third embodiment of the present invention.

[0027] Figure 5 This is a simulation diagram of the relationship between the digital control code and the current amplifier parameters in the third embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0030] "Coupled" or "connected" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrically conductive medium, which may have parasitic inductance or parasitic capacitance; indirect connection may also include connection through other active or passive devices on the basis of achieving the same or similar functional purposes, such as connection through circuits or components such as switches and follower circuits. In addition, in the present invention, words such as "first" and "second" are mainly used to distinguish one technical feature from another technical feature, and do not necessarily require or imply that there is a certain actual relationship, quantity or order between these technical features.

[0031] Example 1

[0032] like Figure 1 As shown, a current amplifier in an embodiment of the present invention includes a current generating unit 1 , a control voltage generating unit 2 , a negative feedback unit 3 and a clamping unit 4 .

[0033] The current generating unit 1 is used to generate the input current Ib. The control voltage generating unit 2 is used to generate the control voltage signal VCTRL. The negative feedback unit 3 is connected to the first end of the current generating unit 1 and the output end of the clamping unit 4. The negative feedback unit 3 is used to generate the control voltage signal VCTRL based on the input current I b and the output current I generated by the clamp unit 4 out The feedback voltage signal VE2 is generated. The first input terminal of the clamping unit 4 is connected to the control voltage generating unit 2 , and the second input terminal is connected to the negative feedback unit 3 . The clamping unit 4 is used to clamp the control voltage signal VCTRL and the feedback voltage signal VE2 .

[0034] like Figure 1As shown, in one embodiment, the current generating unit 1 includes a first current source IB. A first end of the first current source IB is connected to the negative feedback unit 3, and a second end of the first current source IB is connected to the reference potential. The first current source IB is used to generate an input current I with zero temperature drift. b .

[0035] like Figure 1 As shown, further, the negative feedback unit 3 includes a first voltage dividing unit 31 and a second voltage dividing unit 32 .

[0036] The first end of the first voltage dividing unit 31 is connected to the reference potential, the second end of the first voltage dividing unit 31 is connected to the output end of the clamping unit 4, and the first voltage dividing unit 31 is used to adjust the output current I out A first voltage division signal V02 is generated between the output terminal of the first voltage division unit 31 and the second terminal of the first voltage division unit 31 .

[0037] The first end of the second voltage dividing unit 32 is connected to the first end of the current generating unit 1 and the second input end of the clamping unit 4. The second voltage dividing unit 32 is used to generate a voltage based on the input current I b A second voltage-dividing signal is generated between the first end of the second voltage-dividing unit 32 and the second end of the second voltage-dividing unit 32, and the second end of the second voltage-dividing unit 32 is connected to the output end of the first voltage-dividing unit 31 to generate a feedback voltage signal VE2 based on the first voltage-dividing signal V02 and the second voltage-dividing signal at the first end of the second voltage-dividing unit 32. In an optional embodiment, the reference potential is a ground potential.

[0038] In one embodiment, the first voltage divider unit 31 includes a first error amplifier EA1 and a first transistor Q1. The first input terminal of the first error amplifier EA1 is connected to the reference potential, the second input terminal of the first error amplifier EA1 is connected to the first terminal of the first transistor Q1 and the output terminal of the clamping unit 4, the output terminal of the first error amplifier EA1 is connected to the control terminal and the second terminal of the first transistor Q1 and serves as the output terminal of the first voltage divider unit 31, and the control terminal of the first transistor Q1 is connected to the second terminal of the second voltage divider unit 32. In an optional embodiment, the first input terminal of the first error amplifier EA1 is a non-inverting input terminal, and the second input terminal of the first error amplifier EA1 is an inverting input terminal. The first terminal of the first transistor Q1 is an emitter, the second terminal is a collector, and the control terminal is a base.

[0039] It can be understood that the first error amplifier EA1 operates in a negative feedback mode, and the first error amplifier EA1 and the first transistor Q1 form a negative feedback loop. Figure 1As shown, the emitter voltage of the first transistor Q1 (i.e., the first terminal voltage) is VE1. Due to the clamping effect of the first error amplifier EA1, the emitter voltage VE1 of the first transistor Q1 is equal to the reference potential. In this embodiment, the reference potential is the ground potential, so the emitter voltage VE1 of the first transistor Q1 is regarded as 0.

[0040] Since the base and collector of the first transistor Q1 are connected, the current flowing through the first transistor Q1 is the output current I out The voltages of the base and collector of the first transistor Q1 are equal to the first voltage-divided signal V02. Since the emitter voltage VE1 of the first transistor Q1 is regarded as 0, the first voltage difference VBE1 between the base and emitter of the first transistor Q1 is the first voltage-divided signal V02, that is, VBE1=V02-VE1=V02.

[0041] The second voltage-dividing unit 32 includes a second transistor Q2. The control end and the second end of the second transistor Q2 are connected to the second end of the first voltage-dividing unit 31, that is, the control end and the second end of the second transistor Q2 are connected to the control end and the second end of the first transistor Q1. The first end of the second transistor Q2 is connected to the second input end of the clamping unit 4 and the first end of the current generating unit 1. In this embodiment, the first end of the second transistor Q2 is the emitter, the second end is the collector, and the control end is the base. Combined with the above analysis, it can be seen that since the base of the second transistor Q2 is connected to the collector, the current flowing through the second transistor Q2 at this time is the output current I b The second voltage difference VBE2 between the base and the emitter of the second transistor Q2 is the second divided voltage signal. At this time, the voltage of the base and the collector of the second transistor Q2 is equal to the first divided voltage signal V02, that is, VBE2 = the first divided voltage signal V02 - the feedback voltage signal VE2.

[0042] The first transistor Q1 and the second transistor Q2 are bipolar junction transistors (BJTs), so the first transistor Q1 satisfies the following functional relationship: For the second transistor Q2, the following functional relationship is satisfied:

[0043] In the above formula, I S Saturation Current. When the voltage between the base and emitter of a bipolar transistor reaches a certain threshold, the transistor will enter a saturation state, and the current will reach a fixed value, that is, I S In this embodiment, the area ratio of the first transistor Q1 to the second transistor Q2 is set to 1:1, so the saturation current I of the first transistor Q1 is S The saturation current I S equal.

[0044] In the above formula, V T Thermal Voltage refers to the change in base-emitter voltage caused by temperature change. It can be expressed by the following formula: V T = kT / q. Where k is the Boltzmann constant, T is the absolute temperature (in Kelvin), and q is the charge of the electron.

[0045] In summary, the first pressure difference VBE1 and the second pressure difference VBE2 satisfy the following functional relationship:

[0046]

[0047] like Figure 1 As shown, the clamping unit 4 includes a second error amplifier EA2 and an output tube. The first input end of the second error amplifier EA2 is connected to the control voltage generating unit 2 to receive the control voltage signal VCTRL. The second input end of the second error amplifier EA2 is connected to the negative feedback unit 3. The output end of the second error amplifier EA2 is connected to the control end of the output tube and generates a first control signal V01. The first end of the output tube is connected to the reference potential, and the second end of the output tube is connected to the first end of the first transistor Q1 of the negative feedback unit 3. The first control signal V01 is used to control the conduction degree of the output tube. When the output tube is turned on, the current flowing through the output tube is the output current I out .

[0048] In an optional implementation, the first input end of the second error amplifier EA2 is a non-inverting input end, and the second input end of the second error amplifier EA2 is an inverting input end. The first end of the output tube M1 is a source, the second end is a drain, and the control end is a gate. In this embodiment, the output tube M1 is an N-channel MOS tube, and in other implementations, the output tube M1 can be a P-channel MOS tube.

[0049] like Figure 1 As shown, the second error amplifier EA2, the output tube M1 and the negative feedback unit 3 can form a negative feedback loop as a whole. Due to the clamping effect of the second error amplifier EA2, the feedback voltage signal VE2 is equal to the control voltage signal VCTRL, that is,

[0050] It can be seen from the formula that the input current I is established by this embodiment. b With the output current I out The exponential relationship between the saturation current I S In an optional embodiment, the current flowing through the output tube M1 (ie, the output current I out) can be copied or multiplied to achieve the ability to output a current of a specified magnitude.

[0051] like Figure 1 As shown, in one embodiment, the control voltage generating unit 2 includes a second current source 21 and a resistor unit 22. The second current source 21 is connected to a first end of the resistor unit 22 and generates a control voltage signal VCTRL at the first end of the resistor unit 22 based on the current generated by the second current source 21, and a second end of the resistor unit 22 is connected to a reference potential.

[0052] The second current source 21 is a current source that generates a positive temperature coefficient current or a current source that generates a zero temperature drift current. In this embodiment, the second current source 21 is used to generate a positive temperature coefficient current I VT , if the resistance value of the resistor unit 22 is RN, then VCTRL=I VT ·RN. That is, the control voltage signal VCTRL is also a parameter that is positively correlated with the temperature coefficient. It can be understood that the positive temperature coefficient current I VT is positively correlated with the absolute temperature T, then The absolute temperature coefficient T in the formula can be eliminated. This embodiment realizes an exponential amplification relationship between the input current and the output current, while eliminating the influence of PVT.

[0053] Example 2

[0054] like Figure 2 As shown, the difference between this embodiment and embodiment 1 is that the second current source 21 includes a bandgap reference circuit and a sampling resistor R0. The bandgap reference circuit is used to generate a positive temperature coefficient reference voltage k*V T Or zero temperature drift voltage Vz, where k is a fixed coefficient. The sampling resistor R0 is used to adjust the positive temperature coefficient reference voltage k*V T Sampling is performed to obtain the positive temperature coefficient current I VT , or the sampling resistor R0 is used to sample the zero temperature drift voltage Vz to obtain the zero temperature drift current Iz.

[0055] When the second current source 21 generates a positive temperature coefficient current I VT hour, therefore The functional relationship obtained by analyzing according to Example 1 is: available: The input current I of the current amplifier is realized by this embodiment. b With the output current I out There is an exponential amplification relationship between them, and the influence of PVT is eliminated.

[0056] When the second current source 21 is used to generate the zero temperature drift current Iz, based on the above analysis, it can be known that the current amplifier is affected by temperature, and based on this embodiment, an exponential temperature-controlled current output can be achieved.

[0057] Example 3

[0058] like Figure 3 As shown, the difference between this embodiment and embodiment 1 is that the second current source 21 includes a bandgap reference voltage generating unit and a sampling resistor R0, and the resistance value of the resistor unit 22 is adjustable. The bandgap reference voltage generating unit is used to generate the BJT voltage difference k*V in the bandgap reference. T , where k is a fixed coefficient. The sampling resistor R0 is used to adjust the BJT voltage difference k*V T Sampling is performed to obtain the positive temperature coefficient current I VT .

[0059] at this time therefore

[0060] In this embodiment, the resistance unit 22 includes a plurality of first resistors R1 connected in series, in parallel or in mixed connection and corresponding switch units. The resistance unit 22 controls the switch unit through a digital control code CODE to control the number of first resistors R1 connected to the circuit, thereby adjusting the total resistance value of the resistance unit 22. Figure 3 The total resistance of the resistor unit 22 is represented by CODE*R1. The functional relationship obtained by analyzing the embodiment 1 is: available: The total resistance of the resistor unit 22 is adjusted by adjusting the digital control code CODE, thereby realizing a digitally controlled arbitrary exponential current amplifier.

[0061] like Figure 4 As shown, the left figure is the input current I b =100nA, α = 1.05 when the output current and the digital control code CODE function relationship, the right figure is the output current I out The output current is amplified 64 times by the current mirror.

[0062] like Figure 5 As shown, the lower part of the figure is the output current I out Simulation diagram of the change of digital control code CODE. The upper part of the figure is the input current I b When e is a fixed value α The simulation diagram of the digital control code CODE. It can be seen from the figure that e α Almost does not follow the change of the digital control code CODE, that is, the current amplifier proposed in this embodiment realizes the input current I b With the output current I outWhile there is an exponential amplification relationship between them, the impact of PVT is eliminated.

[0063] It is understandable that by setting different parameters in the current amplifier proposed by the present invention as independent variables, different amplification functions can be achieved. For example, in Example 3, the total resistance of the resistor unit 22 is adjusted by a digital control code to achieve a digitally adjustable exponential amplifier. In Example 4, the second current source 21 generates a zero temperature drift current to achieve an exponential temperature-controlled current output. In other embodiments, the input current I b A high-gain exponential current amplifier is realized. It can be understood that the current amplifier proposed by the present invention can set multiple parameters as independent variables at the same time.

[0064] In an optional embodiment, the present invention can also control the positive temperature coefficient current I by an analog circuit. VT Alternatively, the resistance unit 22 may be controlled by an analog circuit.

[0065] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0066] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A current amplifier, characterized in that: The current amplifier comprises a current generating unit, a negative feedback unit, a control voltage generating unit and a clamping unit; The current generating unit is used to generate input current; The control voltage generating unit is used to generate a control voltage signal; The negative feedback unit is connected to the first end of the current generating unit and the output end of the clamping unit, and the negative feedback unit is used to generate a feedback voltage signal based on the input current and the output current generated by the clamping unit; The first input end of the clamping unit is connected to the control voltage generating unit, and the second input end is connected to the negative feedback unit. The clamping unit is used to clamp the control voltage signal and the feedback voltage signal.

2. The current amplifier according to claim 1, characterized in that: The negative feedback unit includes a first voltage dividing unit and a second voltage dividing unit; A first end of the first voltage dividing unit is connected to a reference potential, a second end of the first voltage dividing unit is connected to an output end of the clamping unit, and the first voltage dividing unit is used to generate a first voltage dividing signal between the output end of the first voltage dividing unit and the second end of the first voltage dividing unit based on the output current; The first end of the second voltage divider unit is connected to the first end of the current generating unit and the second input end of the clamping unit, the second voltage divider unit is used to generate a second voltage divider signal between the first end of the second voltage divider unit and the second end of the second voltage divider unit based on the input current, and the second end of the second voltage divider unit is connected to the output end of the first voltage divider unit to generate a feedback voltage signal at the first end of the second voltage divider unit based on the first voltage divider signal and the second voltage divider signal.

3. The current amplifier according to claim 2, characterized in that: The first voltage divider unit includes a first error amplifier and a first transistor, wherein the first input end of the first error amplifier is connected to a reference potential, the second input end of the first error amplifier is connected to the first end of the first transistor and the output end of the clamping unit, the output end of the first error amplifier is connected to the control end and the second end of the first transistor and serves as the output end of the first voltage divider unit, and the control end of the first transistor is connected to the second end of the second voltage divider unit.

4. The current amplifier according to claim 2, characterized in that: The second voltage dividing unit includes a second transistor, the control end and the second end of the second transistor are connected to the output end of the first voltage dividing unit and serve as the second end of the second voltage dividing unit, and the first end of the second transistor is connected to the second input end of the clamping unit and the current generating unit and serves as the first end of the second voltage dividing unit.

5. The current amplifier according to claim 1, characterized in that: The clamping unit includes a second error amplifier and an output tube, wherein the first input end of the second error amplifier is connected to the control voltage generating unit to receive a control voltage signal, the second input end of the second error amplifier is connected to the negative feedback unit, the output end of the second error amplifier is connected to the control end of the output tube and generates a first control signal, the first end of the output tube is connected to a reference potential, the second end of the output tube is connected to the negative feedback unit, and the output tube is used to generate an output current based on the first control signal.

6. The current amplifier according to claim 1, characterized in that: The current generating unit comprises a first current source, a first end of the first current source is connected to the negative feedback unit, and a second end of the first current source is connected to a reference potential.

7. The current amplifier according to claim 1, characterized in that: The control voltage generating unit includes a second current source and a resistance unit, wherein the second current source is connected to a first end of the resistance unit and generates a control voltage signal at the first end of the resistance unit based on a current generated by the second current source, and a second end of the resistance unit is connected to a reference potential.

8. The current amplifier according to claim 7, characterized in that: The second current source is a current source that generates a positive temperature coefficient current or a current source that generates a zero temperature drift current.

9. The current amplifier according to claim 7, characterized in that: The resistance unit includes a plurality of first resistors connected in series, in parallel or in mixed connection and corresponding switch units. The resistance unit controls the switch units through digital control codes to adjust the total resistance value of the resistance unit.

10. A chip, characterized in that: The chip comprises the current amplifier according to any one of claims 1 to 9.

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