CN117200713A - Meter amplifier - Google Patents
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- CN117200713A CN117200713A CN202311056275.2A CN202311056275A CN117200713A CN 117200713 A CN117200713 A CN 117200713A CN 202311056275 A CN202311056275 A CN 202311056275A CN 117200713 A CN117200713 A CN 117200713A
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Abstract
The invention discloses an instrument amplifier, which comprises an input stage circuit, a first output stage circuit and a second output stage circuit, wherein the input stage circuit is used for converting the voltage difference between a first input voltage and a second input voltage into an input current, and the input current is in set proportion to the voltage difference; a first mirror circuit for mirroring the input current to a first mirrored current; a first output circuit connected with the first mirror circuit, wherein the first output circuit includes: the positive input end of the first operational amplifier receives the reference voltage, the negative input end of the first operational amplifier is connected with the first mirror image circuit, and the output end of the first operational amplifier provides a first output voltage; and a first output resistor connected between the negative input terminal and the output terminal of the first operational amplifier, the first output circuit being configured to supply the first mirror current to the first output resistor to obtain the first output voltage related to a voltage difference between the first input voltage and the second input voltage, thereby improving a common mode rejection ratio and increasing an input common mode voltage range.
Description
Technical Field
The invention relates to the technical field of high-precision sensor detection, in particular to an instrument amplifier.
Background
The instrument amplifier is widely used in the fields of industrial signal acquisition, sensor interfaces and the like, and the traditional three-operational amplifier instrument amplifier has high input impedance.
Fig. 1 shows a schematic circuit diagram of an instrumentation amplifier according to the prior art. Fig. 1 shows a three-op-amp instrumentation amplifier most commonly used in the prior art, which uses the forward input ends of two identical operational amplifiers A1 and A2 as differential input ends, and uses two resistors R1 and R2 connected in parallel to the reverse input ends of the two operational amplifiers A1 and A2 as feedback structures to form an input buffer, and uses the output ends of the two operational amplifiers A1 and A2 to be connected to the input end of the operational amplifier A3 through the resistors R3 and R4 respectively, and uses resistors R5 and R6 connected in parallel to the output end of the operational amplifier A3 and the reference voltage Vref as feedback, wherein when r1=r2, r3=r4, and r5=r6, the gain of the instrumentation amplifier is thatWherein vin=vjn1-vjn2. The common-mode input range of the instrument amplifier is influenced by the first-stage gain, when the first-stage gain is high, the common-mode input range is correspondingly reduced, and the common-mode rejection ratio (CMRR) is influenced by the mismatch of output resistors, and if trimming (trim) is not carried out, the common-mode rejection ratio (CMRR) can only reach about 80 dB.
In order to improve the CMRR of the traditional three-operational-amplifier instrument amplifier, the prior art generally adopts trimming of the output-stage resistor, which increases the test cost and has limited trimming precision; to increase its common mode input range, its first stage gain is often set lower, which causes the output stage to distribute more gain but reduces its bandwidth. Therefore, a new instrumentation amplifier has to be proposed to solve the above-mentioned problems.
Disclosure of Invention
In view of the foregoing, it is an object of the present invention to provide an instrumentation amplifier that can increase the input common mode voltage range by increasing the common mode rejection ratio.
According to an aspect of the present invention, there is provided a instrumentation amplifier comprising an input stage circuit for converting a voltage difference of a first input voltage and a second input voltage into an input current, the input current being proportional to the voltage difference; a first mirror circuit for mirroring the input current to a first mirrored current; a first output circuit connected with the first mirror circuit, wherein the first output circuit includes: the positive input end of the first operational amplifier receives the reference voltage, the negative input end of the first operational amplifier is connected with the first mirror image circuit, and the output end of the first operational amplifier provides a first output voltage; and a first output resistor connected between the negative input terminal and the output terminal of the first operational amplifier, the first output circuit configured to supply the first mirror current to the first output resistor to obtain the first output voltage related to a voltage difference between the first input voltage and the second input voltage.
Optionally, the input stage circuit includes: a first input circuit for generating a first follow-up voltage from the first input voltage; a second input circuit for generating a second follow-up voltage from the second input voltage; and the conversion circuit is connected between the first input circuit and the second input circuit and is used for converting the voltage difference between the first following voltage and the second following voltage into the input current, wherein the voltage difference between the first following voltage and the second following voltage is equal to the voltage difference between the first input voltage and the second input voltage.
Optionally, the first input circuit includes: the first chopper comprises a first input end and a second input end, wherein the first input end and the second input end of the first chopper are respectively used for receiving the first input voltage and the first following voltage, and the first output end and the second output end of the first chopper are respectively used for providing the chopped first input voltage and the chopped first following voltage; the positive input end and the negative input end of the first amplifier are respectively connected with the first output end and the second output end of the first chopper; the first control unit is characterized in that a first input end and a second input end of the first control unit are respectively connected with a positive output end and a negative output end of the first amplifier, and the output ends of the first control unit provide a first control signal; the input end of the first output unit is connected with the output end of the first control unit, and the output end of the first output unit provides the first following voltage; the second input circuit includes: the first input end and the second input end of the second chopper are respectively used for receiving the second input voltage and the second following voltage, and the first output end and the second output end of the second chopper are respectively used for providing the chopped second input voltage and the chopped second following voltage; the positive input end and the negative input end of the second amplifier are respectively connected with the first output end and the second output end of the second chopper; the first input end and the second input end of the second control unit are respectively connected with the positive output end and the negative output end of the second amplifier, and the output end of the second control unit provides a second control signal; the input end of the second output unit is connected with the output end of the second control unit, and the output end of the second output unit provides the second following voltage; the conversion circuit includes: and the two ends of the input resistor are respectively connected with the output ends of the first output unit and the second output unit, and the input current flows through the input resistor.
Optionally, the first output unit includes: the first resistor, the first transistor of the first doping type, the second transistor of the second doping type and the third resistor are sequentially connected between the power supply voltage and the reference ground, wherein the first transistor is connected with the grid electrode of the second transistor, the first transistor is connected with the drain electrode of the second transistor, the grid electrode of the first transistor is the input end of the first output unit, and the drain electrode of the first transistor is the output end of the first output unit; the second output unit includes: the power supply circuit comprises a fifth resistor, a third transistor of a first doping type, a fourth transistor of a second doping type and a seventh resistor which are sequentially connected between a power supply voltage and a reference ground, wherein the third transistor is connected with a grid electrode of the fourth transistor, the third transistor is connected with a drain electrode of the fourth transistor, the grid electrode of the third transistor is an input end of the second output unit, and the drain electrode of the third transistor is an output end of the second output unit.
Optionally, the first mirror circuit includes: the first transconductance operational amplifier and the second transconductance operational amplifier are connected between a power supply voltage and a reference ground in sequence, wherein the drain electrode of the first transconductance operational amplifier is connected with the drain electrode of the first transconductance operational amplifier; the positive input end of the first transconductance operational amplifier is connected with the common node of the second resistor and the fifth transistor, the negative input end of the first transconductance operational amplifier is connected with the common node of the first resistor and the first transistor, and the output end of the first transconductance operational amplifier is connected with the grid electrode of the fifth transistor; the positive input end of the second transconductance operational amplifier is connected with a common node of the fourth resistor and the sixth transistor, the negative input end of the second transconductance operational amplifier is connected with a common node of the third resistor and the second transistor, the output end of the second transconductance operational amplifier is connected with the grid electrode of the sixth transistor, the resistance values of the first resistor and the second resistor are equal, and the resistance values of the third resistor and the fourth resistor are equal.
Optionally, the instrumentation amplifier further comprises: a second mirror circuit for mirroring the input current to a second mirrored current; and a second output voltage connected to the second mirror circuit, wherein the second output circuit includes: the positive input end of the second operational amplifier receives the reference voltage, the negative input end of the second operational amplifier is connected with the second mirror circuit, and the output end of the second operational amplifier provides a second output voltage; and a second output resistor connected between the negative input terminal and the output terminal of the second operational amplifier, the second output circuit configured to supply the second mirror current to the second output resistor to generate the second output voltage.
Optionally, the resistances of the first output resistor and the second output resistor are equal, and the voltage difference between the first output voltage and the second output voltage is set proportional to the voltage difference between the first input voltage and the second input voltage.
Optionally, the second mirroring circuit includes: the third transconductance operational amplifier and the fourth transconductance operational amplifier are sequentially connected with a sixth resistor, a seventh transistor of a first doping type, an eighth transistor of a second doping type, an eighth resistor, a third transconductance operational amplifier and a fourth transconductance operational amplifier between a power supply voltage and a reference ground, wherein the drain electrodes of the seventh transistor and the eighth transistor are connected, and the drain electrode of the seventh transistor is the output end of the second mirror circuit; the positive input end of the third transconductance operational amplifier is connected with the common node of the sixth resistor and the seventh transistor, the negative input end of the third transconductance operational amplifier is connected with the common node of the fifth resistor and the third transistor, and the output end of the third transconductance operational amplifier is connected with the grid electrode of the seventh transistor; the positive input end of the fourth transconductance operational amplifier is connected with a common node of the eighth resistor and the eighth transistor, the negative input end of the fourth transconductance operational amplifier is connected with the common node of the seventh resistor and the fourth transistor, the output end of the fourth transconductance operational amplifier is connected with the grid electrode of the eighth transistor, the resistance values of the fifth resistor and the sixth resistor are equal, and the resistance values of the seventh resistor and the eighth resistor are equal.
Optionally, the first doping type is P-type doping, and the second doping type is N-type doping.
Optionally, the first operational amplifier and the second operational amplifier are chopper operational amplifiers, the first amplifier and the second amplifier are chopper amplifiers, and the first to fourth transconductance operational amplifiers are chopper transconductance operational amplifiers.
According to the instrument amplifier provided by the embodiment of the invention, the voltage difference between the first input voltage and the second input voltage is converted into the input current, and the input current is mirrored, so that the input current flows through the output resistor to generate the output voltage, the influence of the common mode voltage on the output voltage is eliminated, the CMRR of the instrument amplifier is greatly improved, the CMRR can reach more than 120dB even if trimming is not performed, and the gain of the instrument amplifier does not influence the common mode input range because the first input circuit and the second input circuit adopt the operational amplifier serving as a voltage follower.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 shows a schematic circuit diagram of an instrumentation amplifier according to the prior art;
fig. 2 shows a schematic block diagram of a instrumentation amplifier according to a first embodiment of the present invention;
fig. 3 shows a circuit schematic of an instrumentation amplifier according to a first embodiment of the present invention;
fig. 4 shows a schematic block diagram of a instrumentation amplifier according to a second embodiment of the present invention;
fig. 5 shows a circuit schematic of an instrumentation amplifier according to a second embodiment of the present invention.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. The same elements or modules are denoted by the same or similar reference numerals in the various figures. For clarity, the various features of the drawings are not drawn to scale.
It should be appreciated that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and/or elements capable of storing instructions for execution by the programmable circuits. When an element or circuit is referred to as being "connected to" another element or circuit is "connected between" two nodes, it can be directly coupled or connected to the other element or intervening elements may be present, the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements present between the two.
Also, certain terms are used throughout the description and claims to refer to particular components. It will be appreciated by those of ordinary skill in the art that a hardware manufacturer may refer to the same component by different names. The present patent specification and claims do not take the form of an element or components as a functional element or components as a rule.
Furthermore, it should be noted that relational terms such as first and second are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Fig. 2 shows a schematic block diagram of a instrumentation amplifier according to an embodiment of the present invention. Referring to fig. 2, the instrumentation amplifier 1000 includes: the first input circuit 110, the second input circuit 210, the first mirror circuit 120, the first output circuit 130, and the conversion circuit 300.
The first input circuit 110, the second input circuit 210, and the conversion circuit 300 are input stage circuits of the instrumentation amplifier 1000, the input stage circuits are configured to convert a voltage difference between the first input voltage Vin1 and the second input voltage Vin2 into an input current Ig, the input current Ig is in a set proportion to the voltage difference, and the first mirror circuit 120 is configured to mirror the input current Ig onto an output resistor of the first output circuit 130 in equal proportion to obtain an output voltage Vo1 related to the voltage difference between the first input voltage Vin1 and the second input voltage Vin2.
Specifically, the first input circuit 110 has a first input terminal, a second input terminal, and a first output terminal, wherein the first input terminal receives the first input voltage Vin1, the second input terminal is connected to the first output terminal, and the first output terminal provides the first follower voltage. The first input circuit 110 is configured to generate a first follow voltage from a first input voltage Vin 1.
The second input circuit 210 has a first input terminal receiving the second input voltage Vin2, a second input terminal connected to the first output terminal, and a first output terminal providing the second follow voltage. The second input circuit 210 is configured to generate a second follow voltage from the second input voltage Vin2. Wherein, the voltage difference between the first following voltage and the second following voltage is equal to the voltage difference between the first input voltage Vin1 and the second input voltage Vin2.
The conversion circuit 300 is connected to the first output terminal of the first input circuit 110 and the first output terminal of the second input circuit 210, and is configured to convert a voltage difference between the first following voltage and the second following voltage into an input current Ig.
In addition, the first input circuit 110 further has a second output terminal and a third output terminal for providing a first voltage and a second voltage, respectively; the second input circuit 210 further has a second output terminal and a third output terminal for providing a third voltage and a fourth voltage, respectively.
The first mirror circuit 120 has a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal and the second input terminal are respectively connected to the second output terminal and the third output terminal of the first input circuit 110, and the output terminal provides the first mirror current I1. The first mirror circuit 120 is configured to mirror the input current Ig according to the first voltage and the second voltage to generate a first mirror current I1. Wherein the first mirror current I1 is equal to the input current Ig.
The first output circuit 130 has a first input terminal receiving the first mirror current I1, a second input terminal receiving the reference voltage Vref, and an output terminal providing the output voltage Vo1. The first output circuit 130 is configured to generate the output voltage Vo1 according to the first mirror current I1 and the reference voltage Vref.
In the instrumentation amplifier 1000, the first input circuit 110 and the second input circuit 210 may be regarded as operational amplifiers functioning as voltage followers, and a voltage difference between a first follower voltage output from the first input circuit 110 and a second follower voltage output from the second input circuit 210 is equal to a voltage difference between the first input voltage Vin1 and the second input voltage Vin2. The relation between the first input voltage Vin1 and the second input voltage Vin2 can be Vin1 > Vin2, or can be Vin1 < Vin2, and the direction of the input current Ig is influenced by the magnitude relation between the first input voltage Vin1 and the second input voltage Vin2.
The instrumentation amplifier 1000 converts the voltage difference between the first input voltage Vin1 and the second input voltage Vin2 into the input current Ig, mirrors the input current Ig into the first mirror current I1 in equal proportion, and finally generates the output voltage Vo1 according to the first mirror current I1, thereby eliminating the influence of the common mode voltage on the output voltage Vo1, greatly improving the CMRR of the instrumentation amplifier 1000, and reaching more than 120dB even without trimming, and since the first input circuit 110 and the second input circuit 210 adopt the operational amplifier serving as a voltage follower, the gain of the instrumentation amplifier 1000 does not affect the common mode input range.
Fig. 3 shows a circuit schematic of an instrumentation amplifier according to a first embodiment of the present invention. Referring to fig. 3, the first input circuit 110 includes a chopper 111, an amplifier 112, a control unit 113, and an output unit 114, the amplifier 112 is an input stage of the first input circuit 110, the control unit 113 is used for controlling the output unit 114, and the control unit 113 generally controls the output unit 114 by using a linear transconductance loop.
The first input end and the second input end of the chopper 111 are respectively a first input end and a second input end of the first input circuit 110, the first output end and the second output end of the chopper 111 are respectively connected with a positive input end and a negative input end of the amplifier 112, the positive output end and the negative output end of the amplifier 112 are respectively connected with a first input end and a second input end of the control unit 113, an output end of the control unit 113 is connected with an input end of the output unit 114, and an output end of the output unit 114 is a first output end of the first input circuit 110. The first input voltage Vin1 and the first following voltage received by the first input terminal and the second input terminal of the first input circuit 110 are chopped by the chopper 111, amplified by the amplifier 112, and provided to the control unit 113, and the control unit 113 provides a control signal to the output unit 114, so that the output unit 114 provides the first following voltage, thereby forming a feedback loop.
The output unit 114 adopts a classAB output stage, the output unit 114 includes a resistor R1, a transistor MP1, a transistor MN1, and a resistor R3 sequentially connected between a power supply voltage VDD and a reference ground, the transistor MP1 is connected to a gate of the transistor MN1, the gate of the transistor MP1 is an input terminal of the output unit 114, the transistor MP1 is connected to a drain terminal of the transistor MN1, a drain terminal of the transistor MP1 is an output terminal of the output unit 114, a common node of the resistor R1 and the transistor MP1 is a second output terminal of the first input circuit 110, and a common node of the transistor MN1 and the resistor R3 is a third output terminal of the first input circuit 110. The classAB output stage includes a transistor MP1 and a transistor MN1.
The second input circuit 210 includes a chopper 211, an amplifier 212, a control unit 213, and an output unit 214, the amplifier 212 is an input stage of the first input circuit 210, the control unit 213 is used for controlling the output unit 214, and the control unit 213 generally controls the output unit 214 by using a linear transconductance loop.
The first input end and the second input end of the chopper 211 are the first input end and the second input end of the second input circuit 210, respectively, the first output end and the second output end of the chopper 211 are connected to the positive input end and the negative input end of the amplifier 212, respectively, the positive output end and the negative output end of the amplifier 212 are connected to the first input end and the second input end of the control unit 213, respectively, the output end of the control unit 213 is connected to the input end of the output unit 214, and the output end of the output unit 214 is the first output end of the second input circuit 210. The first input terminal and the second input terminal of the second input circuit 210 receive the second input voltage Vin2 and the second following voltage, which are chopped by the chopper 211 and amplified by the amplifier 212, and then provided to the control unit 213, and the control unit 213 provides a control signal to the output unit 214, so that the output unit 214 provides the second following voltage, thereby forming a feedback loop.
The output unit 214 adopts a classAB output stage, the output unit 214 includes a resistor R5, a transistor MP3, a transistor MN3, and a resistor R7 sequentially connected between the power supply voltage VDD and the reference ground, the transistor MP3 is connected to the gate of the transistor MN3, the gate of the transistor MP3 is an input terminal of the output unit 214, the drain of the transistor MP3 is an output terminal of the output unit 214, a common node of the resistor R5 and the transistor MP3 is a second output terminal of the second input circuit 210, and a common node of the transistor MN3 and the resistor R7 is a third output terminal of the second input circuit 210. The classAB output stage includes a transistor MP3 and a transistor MN3.
The conversion circuit 300 includes, for example, an input resistor Rg, two ends of the input resistor Rg are respectively connected to a first following voltage and a second following voltage, and a current flowing through the input resistor Rg is an input current Ig. Assuming that in the present embodiment, the second input voltage Vin2 is greater than the first input voltage Vin1, the formula of the input current Ig is:
Ig＝(Vin2-Vin1)/Rg。
providing choppers 111 and 211 at the inputs of the first input circuit 110 and the second input circuit 210, respectively, results in very small offset voltages and very low frequency noise.
Further, both amplifier 112 and amplifier 212 are chopper amplifiers, which may further result in smaller offset voltages and lower low frequency noise.
The first mirror circuit 120 includes a resistor R2, a transistor MP2, a transistor MN2, a resistor R4, and transconductance operational amplifiers OTA1 and OTA2 sequentially connected between the power supply voltage VDD and the reference ground, where the resistance of the resistor R2 is equal to the resistance of the resistor R1, and the resistance of the resistor R3 is equal to the resistance of the resistor R4.
The common node of the transistors MP2 and MN2 is an output end of the first mirror circuit 120, the positive input terminal of the transconductance operational amplifier OTA1 is connected to the resistor R2 and the common node of the transistor MP2, the negative input terminal of the transconductance operational amplifier OTA1 is used as the first input terminal of the first mirror circuit 120 to receive the first voltage, and the output terminal of the transconductance operational amplifier OTA1 is connected to the control terminal of the transistor MP 2. The positive input terminal of the transconductance operational amplifier OTA2 is connected to the common node of the resistor R4 and the transistor MN2, the negative input terminal of the transconductance operational amplifier OTA2 is used as the second input terminal of the first mirror circuit 120 to receive the second voltage, and the output terminal of the transconductance operational amplifier OTA2 is connected to the control terminal of the transistor MN 2. The first mirror circuit 120 uses the transconductance operational amplifier OTA1 to clamp the common node voltage of the resistor R2 and the transistor MP2 at the first voltage, so that the voltage drops at the two ends of the resistor R1 and the resistor R2 are equal, and uses the transconductance operational amplifier OTA2 to clamp the common node voltage of the resistor R4 and the transistor MN2 at the second voltage, so that the voltage drops at the two ends of the resistor R3 and the resistor R4 are equal, so that the input current Ig is mirrored as the first mirror current I1 in equal proportion.
Further, the transconductance operational amplifiers OTA1 and OTA2 employ chopped transconductance operational amplifiers, so that the mirror image of the input current Ig is more accurate.
The first output circuit 130 includes an operational amplifier 131 and an output resistor Ro1 disposed between a negative input terminal and an output terminal of the operational amplifier 131, wherein the negative input terminal of the operational amplifier 131 is connected to the output terminal of the first mirror circuit 120, the positive input terminal of the operational amplifier 131 receives a reference voltage Vref (the voltage value of the reference voltage Vref is not specifically limited, for example, VDD/2), the output terminal of the operational amplifier 131 provides an output voltage Vo1, and the output voltage Vo1 has the formula:
Vo1＝Vref+(Ro1/Rg)*(Vin2-Vin1)。
further, the operational amplifier 131 is a chopper operational amplifier.
Optionally, the transistors MP1-MP3 are doped P-type and the transistors MN1-MN3 are doped N-type.
The gain of the instrumentation amplifier 1000 is Ro1/Rg, and as can be seen by the formula, the output voltage Vo1 of the instrumentation amplifier 1000 is not affected by the resistance matching.
According to the instrument amplifier 1000 provided by the embodiment of the invention, the voltage difference between the first input voltage Vin1 and the second input voltage Vin2 is converted into the input current Ig, the input current Ig is mirrored into the first mirrored current I1 in an equal proportion, and finally the first mirrored current I1 flows through the resistor Ro1 to generate the output voltage Vo1, so that the influence of the common mode voltage on the output voltage Vo1 is eliminated, the CMRR of the instrument amplifier 1000 is greatly improved, the CMRR can reach more than 120dB even if trimming is not performed, and the gain of the instrument amplifier 1000 does not influence the common mode input range because the first input circuit 110 and the second input circuit 210 adopt the operational amplifier serving as a voltage follower.
The instrumentation amplifier 1000 provided in the first embodiment of the present invention adopts a differential input single-ended output structure, but the present invention is not limited thereto, and the present invention is equally applicable to an instrumentation amplifier of differential input differential output.
Fig. 4 shows a schematic block diagram of a instrumentation amplifier according to a second embodiment of the present invention. Referring to fig. 4 and 2, the instrumentation amplifier 2000 according to the second embodiment of the present invention is different from the instrumentation amplifier 1000 according to the first embodiment of the present invention only in that the instrumentation amplifier 2000 has the second mirror circuit 220 and the second output circuit 230 added thereto on the basis of the instrumentation amplifier 1000, thereby realizing differential output. The following description of the same points will not be repeated, but only the differences between the two points will be described.
Referring to fig. 4, the second mirror circuit 220 has a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal and the second input terminal are respectively connected to the second output terminal and the third output terminal of the second input circuit 210, and the output terminal provides the second mirror current I2. The second mirroring circuit 220 is configured to mirror the input current Ig according to the third voltage and the fourth voltage to generate a second mirrored current I2. Wherein the second mirror current I2 is equal to the input current Ig.
The second output circuit 230 has a first input terminal receiving the second mirror current I2, a second input terminal receiving the reference voltage Vref, and an output terminal providing the output voltage Vo2. The second output circuit 230 is configured to generate the output voltage Vo2 according to the second mirror current I2 and the reference voltage Vref.
Fig. 5 shows a circuit schematic of an instrumentation amplifier according to a second embodiment of the present invention.
Referring to fig. 5, the second mirror circuit 220 includes a resistor R6, a transistor MP4, a transistor MN4, a resistor R8, and transconductance operational amplifiers OTA3 and OTA4 connected in sequence between the power supply voltage VDD and ground.
The common node of the transistors MP4 and MN4 is an output end of the second mirror circuit 220, the positive input terminal of the transconductance operational amplifier OTA3 is connected to the resistor R4 and the common node of the transistor MP4, the negative input terminal of the transconductance operational amplifier OTA3 is connected to the first input end of the second mirror circuit 220 to receive the third voltage, and the output terminal of the transconductance operational amplifier OTA3 is connected to the control end of the transistor MP 4. The positive input end of the transconductance operational amplifier OTA4 is connected with a common node of the resistor R8 and the transistor MN4, the negative input end of the transconductance operational amplifier OTA4 is connected with a first input end of the second mirror circuit 220 to receive the fourth voltage, and the output end of the transconductance operational amplifier OTA4 is connected with the control end of the transistor MN 4. The second mirror circuit 220 uses the transconductance operational amplifier OTA3 to place the common node voltage clamp of the resistor R6 and the transistor MP4 at the third voltage, so that the voltage drops at the two ends of the resistor R5 and the resistor R6 are equal, and uses the transconductance operational amplifier OTA4 to place the common node voltage clamp of the resistor R8 and the transistor MN4 at the fourth voltage, so that the voltage drops at the two ends of the resistor R7 and the resistor R8 are equal, so as to mirror the input current Ig into the second mirror current I2 in equal proportion.
Further, the transconductance operational amplifiers OTA3 and OTA4 employ chopped transconductance operational amplifiers, so that the input current Ig mirror image is more accurate.
Optionally, the doping type of the transistor MP4 is P-type doping, and the doping type of the transistor MN4 is N-type doping.
The second output circuit 230 includes an operational amplifier 231 and an output resistor Ro2 disposed between a negative input terminal and an output terminal of the operational amplifier 231, wherein the negative input terminal of the operational amplifier 231 is connected to the output terminal of the second mirror circuit 220, the positive input terminal of the operational amplifier 231 receives the reference voltage Vref (the voltage value of the reference voltage Vref is not specifically limited in the present invention, for example, is 0), and the output terminal of the operational amplifier 231 provides the output voltage Vo2. The output voltage Vo2 and the output voltage Vo1 are differential voltages, and the resistances of the output resistor Ro1 and the output resistor Ro2 are equal.
In this embodiment, assuming that the first input voltage Vin1 is smaller than the second input voltage Vin2, the formula of the final output voltage Vo of the instrumentation amplifier 2000 is:
Vo＝Vo1-Vo2＝2(Ro1/Rg)*(Vin2-Vin1)。
the gain of the instrumentation amplifier 2000 is 2Ro1/Rg, and as can be seen from the formula, the output voltage Vo of the instrumentation amplifier 2000 is not affected by the resistance matching.
According to the instrument amplifier 2000 provided by the embodiment of the invention, the voltage difference between the first input voltage Vin1 and the second input voltage Vin2 is converted into the input current Ig, the input current Ig is mirrored into the first mirrored current I1 and the second mirrored current I2 in a uniform proportion, and finally the first mirrored current I1 and the second mirrored current I2 respectively flow through the output resistor Ro1 and the output resistor Ro2, so that the operation of differential output voltages Vo1 and Vo2 is generated, the influence of the common-mode voltage on the output voltage Vo is eliminated, the CMRR of the instrument amplifier 1000 is greatly improved, the CMRR can reach more than 120dB even if trimming is not performed, and the gain of the instrument amplifier 2000 does not influence the common-mode input range because the first input circuit 110 and the second input circuit 210 adopt the operational amplifier serving as a voltage follower.
Embodiments in accordance with the present invention, as described above, are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various modifications as are suited to the particular use contemplated. The scope of the invention should be determined by the appended claims and their equivalents.
Claims (10)
1. An instrumentation amplifier, comprising:
an input stage circuit for converting a voltage difference of a first input voltage and a second input voltage into an input current, the input current being proportional to the voltage difference;
a first mirror circuit for mirroring the input current to a first mirrored current;
a first output circuit connected to the first mirror circuit,
wherein the first output circuit includes:
the positive input end of the first operational amplifier receives the reference voltage, the negative input end of the first operational amplifier is connected with the first mirror image circuit, and the output end of the first operational amplifier provides a first output voltage; and
a first output resistor connected between the negative input end and the output end of the first operational amplifier,
the first output circuit is configured to provide the first mirrored current to the first output resistor to obtain the first output voltage related to a voltage difference of the first input voltage and the second input voltage.
2. The instrumentation amplifier of claim 1, wherein the input stage circuit comprises:
a first input circuit for generating a first follow-up voltage from the first input voltage;
a second input circuit for generating a second follow-up voltage from the second input voltage;
a conversion circuit connected between the first input circuit and the second input circuit for converting a voltage difference between the first follower voltage and the second follower voltage into the input current,
wherein a voltage difference between the first following voltage and the second following voltage is equal to a voltage difference between the first input voltage and the second input voltage.
3. The instrumentation amplifier according to claim 2, wherein,
the first input circuit includes:
the first chopper comprises a first input end and a second input end, wherein the first input end and the second input end of the first chopper are respectively used for receiving the first input voltage and the first following voltage, and the first output end and the second output end of the first chopper are respectively used for providing the chopped first input voltage and the chopped first following voltage;
the positive input end and the negative input end of the first amplifier are respectively connected with the first output end and the second output end of the first chopper;
the first control unit is characterized in that a first input end and a second input end of the first control unit are respectively connected with a positive output end and a negative output end of the first amplifier, and the output ends of the first control unit provide a first control signal;
the input end of the first output unit is connected with the output end of the first control unit, and the output end of the first output unit provides the first following voltage;
the second input circuit includes:
the first input end and the second input end of the second chopper are respectively used for receiving the second input voltage and the second following voltage, and the first output end and the second output end of the second chopper are respectively used for providing the chopped second input voltage and the chopped second following voltage;
the positive input end and the negative input end of the second amplifier are respectively connected with the first output end and the second output end of the second chopper;
the first input end and the second input end of the second control unit are respectively connected with the positive output end and the negative output end of the second amplifier, and the output end of the second control unit provides a second control signal;
the input end of the second output unit is connected with the output end of the second control unit, and the output end of the second output unit provides the second following voltage;
the conversion circuit includes:
and the two ends of the input resistor are respectively connected with the output ends of the first output unit and the second output unit, and the input current flows through the input resistor.
4. The instrumentation amplifier of claim 3, wherein,
the first output unit includes:
a first resistor, a first transistor of a first doping type, a second transistor of a second doping type, a third resistor connected in sequence between the supply voltage and the reference ground,
wherein the first transistor is connected with the grid electrode of the second transistor, the drain electrode of the first transistor is connected with the drain electrode of the second transistor,
the grid of the first transistor is an input end of the first output unit, and the drain electrode of the first transistor is an output end of the first output unit;
the second output unit includes:
a fifth resistor, a third transistor of the first doping type, a fourth transistor of the second doping type, a seventh resistor connected in sequence between the supply voltage and the reference ground,
wherein the third transistor is connected with the grid electrode of the fourth transistor, the third transistor is connected with the drain electrode of the fourth transistor,
the gate of the third transistor is an input end of the second output unit, and the drain of the third transistor is an output end of the second output unit.
5. The instrumentation amplifier according to claim 4, wherein the first mirror circuit comprises:
a second resistor, a fifth transistor of the first doping type, a sixth transistor of the second doping type, a fourth resistor, a first transconductance operational amplifier and a second transconductance operational amplifier connected in sequence between the power supply voltage and the reference ground,
the drain electrode of the fifth transistor is connected with the drain electrode of the sixth transistor, and the drain electrode of the fifth transistor is the output end of the first mirror circuit;
the positive input end of the first transconductance operational amplifier is connected with the common node of the second resistor and the fifth transistor, the negative input end of the first transconductance operational amplifier is connected with the common node of the first resistor and the first transistor, and the output end of the first transconductance operational amplifier is connected with the grid electrode of the fifth transistor;
the positive input end of the second transconductance operational amplifier is connected with the common node of the fourth resistor and the sixth transistor, the negative input end of the second transconductance operational amplifier is connected with the common node of the third resistor and the second transistor, the output end of the second transconductance operational amplifier is connected with the grid electrode of the sixth transistor,
the resistance values of the first resistor and the second resistor are equal, and the resistance values of the third resistor and the fourth resistor are equal.
6. The instrumentation amplifier according to claim 5, further comprising:
a second mirror circuit for mirroring the input current to a second mirrored current;
a second output voltage connected to the second mirror circuit,
wherein the second output circuit includes:
the positive input end of the second operational amplifier receives the reference voltage, the negative input end of the second operational amplifier is connected with the second mirror circuit, and the output end of the second operational amplifier provides a second output voltage; and
a second output resistor connected between the negative input end and the output end of the second operational amplifier,
the second output circuit is configured to provide the second mirrored current to the second output resistor to generate the second output voltage.
7. The instrumentation amplifier according to claim 6, wherein the first output resistor and the second output resistor have equal resistance values, and the voltage difference of the first output voltage and the second output voltage is set proportional to the voltage difference of the first input voltage and the second input voltage.
8. The instrumentation amplifier according to claim 6, wherein the second mirror circuit comprises:
a sixth resistor, a seventh transistor of the first doping type, an eighth transistor of the second doping type, an eighth resistor, a third transconductance operational amplifier and a fourth transconductance operational amplifier connected in sequence between the power supply voltage and the reference ground,
the drain electrode of the seventh transistor is connected with the drain electrode of the eighth transistor, and the drain electrode of the seventh transistor is the output end of the second mirror circuit;
the positive input end of the third transconductance operational amplifier is connected with the common node of the sixth resistor and the seventh transistor, the negative input end of the third transconductance operational amplifier is connected with the common node of the fifth resistor and the third transistor, and the output end of the third transconductance operational amplifier is connected with the grid electrode of the seventh transistor;
the positive input end of the fourth transconductance operational amplifier is connected with the common node of the eighth resistor and the eighth transistor, the negative input end of the fourth transconductance operational amplifier is connected with the common node of the seventh resistor and the fourth transistor, the output end of the fourth transconductance operational amplifier is connected with the grid electrode of the eighth transistor,
the resistance values of the fifth resistor and the sixth resistor are equal, and the resistance values of the seventh resistor and the eighth resistor are equal.
9. The instrumentation amplifier according to claim 8, wherein the first doping type is a P-type doping and the second doping type is an N-type doping.
10. The instrumentation amplifier of claim 8, wherein the first and second operational amplifiers are chopped operational amplifiers, the first and second amplifiers are chopped amplifiers, and the first through fourth transconductance operational amplifiers are chopped transconductance operational amplifiers.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311056275.2A CN117200713A (en) | 2023-08-21 | 2023-08-21 | Meter amplifier |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311056275.2A CN117200713A (en) | 2023-08-21 | 2023-08-21 | Meter amplifier |
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| CN117200713A true CN117200713A (en) | 2023-12-08 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117518042A (en) * | 2024-01-05 | 2024-02-06 | 赛卓电子科技(上海)股份有限公司 | Output stage circuit and sensor |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117518042A (en) * | 2024-01-05 | 2024-02-06 | 赛卓电子科技(上海)股份有限公司 | Output stage circuit and sensor |
| CN117518042B (en) * | 2024-01-05 | 2024-04-30 | 赛卓电子科技(上海)股份有限公司 | Output stage circuit and sensor |
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