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CN110048683A - A kind of chopper current feedback magnifier of low noise - Google Patents

A kind of chopper current feedback magnifier of low noise Download PDF

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Publication number
CN110048683A
CN110048683A CN201910407883.0A CN201910407883A CN110048683A CN 110048683 A CN110048683 A CN 110048683A CN 201910407883 A CN201910407883 A CN 201910407883A CN 110048683 A CN110048683 A CN 110048683A
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China
Prior art keywords
pmos transistor
resistor
pmos
transistor
nmos
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Inventor
王巍
王伊昌
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Chongqing Yuhu Core Technology Co Ltd
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Chongqing Yuhu Core Technology Co Ltd
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Priority to CN201910407883.0A priority Critical patent/CN110048683A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback
    • H03F1/342—Negative-feedback-circuit arrangements with or without positive feedback in field-effect transistor amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45179—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using MOSFET transistors as the active amplifying circuit

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)

Abstract

A kind of low noise chopper current feedback magnifier, including current feedback amplifying circuit, remnants ripple filter circuit is claimed in the present invention.The current feedback amplifying circuit is by modulation chopper CH1, it inputs mutual conductance Gm1, feedback mutual conductance Gm2, modulation chopper CH2, demodulation chopper CH3, modulation chopper CH4, common source and common grid amplifier A1, demodulation chopper CH5, output amplifier A2, input resistance Rin, output resistance Ro, miller-compensated resistance Rm and miller-compensated electric capacity Cm to constitute, the remnants ripple filter circuit is made of filter resistance R1, R2, filter capacitor C1, C2 and filtering trsanscondutance amplifier.The present invention is by being bonded current feedback structure for input amplifying circuit and current feedback loop, 1/f noise is efficiently reduced by two-stage copped wave structure, by the residual noise filter circuit of design effectively reduce as with output ripple amplitude caused by copped wave, optimize integrated circuit precision.

Description

Low-noise chopper current feedback instrument amplifying circuit
Technical Field
The invention belongs to the field of analog integrated circuit design, and particularly relates to a design of a low-noise chopper current feedback type instrument amplifier circuit.
Background
With the rapid development of wearable electronic products and internet of things (IoT) technologies, more and more practical applications require low-frequency signal measurement devices, such as electroencephalograms, electrocardiograms, electromyograms and other biological signals, which need to be converted into electrical signals through sensors for detection. These biological signals are very weak, on the order of tens to tens, and provide frequencies ranging from dc to hundreds, and at such low frequencies, they are usually affected by non-ideal factors such as 1/f noise and offset voltage, which have proven to be quite disadvantageous for signal acquisition, so that it is necessary to adopt appropriate techniques to eliminate these non-ideal factors and process the weak biological signals. To implement multi-electrode, wearable, implantable applications, the signal acquisition circuitry must have sufficiently low power consumption, which undoubtedly requires low power consumption and high precision Instrumentation Amplifier (IA) circuitry. The IA is used as the analog front end of the acquisition system and plays a role in acquiring and amplifying biological signals, and the quality of the performance of the IA can have great influence on the whole acquisition system. Therefore, a good performance instrumentation amplifier circuit is urgently needed.
Fig. 1 shows a typical instrumentation amplifier application scenario. The patient can gather the ECG signal through the portable ECG signal collection system's that figure 1 shows external sensor to via this article IA carries out accurate amplification, then handles analog signal through the system and uploads the result to "high in the clouds" at last, sends for hospital doctor via "high in the clouds" and carries out the analysis after, uploads the result to high in the clouds again, returns and looks over the result for the patient through the cell-phone.
Fig. 2 is a conventional CMOS instrumentation amplifier, and its basic idea is to use the positive input terminals of two identical operational amplifiers a1, a2 as differential inputs, connect two resistors R1, R2 in parallel as feedback structures to form input buffers at the inverting input terminals of two operational amplifiers a1, a2, and connect the output terminals of operational amplifiers a1, a2 to the input terminal of operational amplifier A3 through resistors R3, R4, and connect resistors R5, R6 in parallel at the output terminal of operational amplifier A3 and the reference voltage Vref end for feedback, when R1 ═ R2, R3 ═ R4, R5 ═ R6, the GAIN of the triple operational amplifier instrumentation amplifier can be obtained as:in the formula, VinIs an outputDifferential Voltage (Vin1-Vin2), R1Is the resistance value of the resistor R1, RgIs the resistance value of the resistor Rg, R5Is the resistance value of the resistor R5, R3Is the resistance value of the resistor R3. The three-operational-amplifier instrumentation amplifier is very dependent on resistance matching, and if the resistance is mismatched, the common-mode rejection performance of the whole circuit is greatly influenced. The problems of low Common Mode Rejection Ratio (CMRR), poor noise performance and the like in the conventional IA circuit design are solved.
Compared with the patent number 201410518644.X, 1. although all adopted the current feedback structure, this circuit design more is fit for working under low voltage, has reduced whole system power consumption, and this circuit has adopted second grade chopper structure and current feedback structure to combine together simultaneously, has realized comparatively good noise performance, has wholly realized comparatively good circuit performance. 2. Compared with the capacitor as feedback, the whole chip area can be reduced by using the resistor as feedback, and meanwhile, the gain is more flexibly set. 3. Because of the influence of the chopping effect, ripples appear in a high-frequency band in an output signal, although the effect of ripple elimination in a feedback loop is good, the structure of the ripple elimination filter is complex, and the stability of the whole system is affected, and a second-order Sallen-Key low-pass filter structure is used in the design of the filter circuit for eliminating the residual ripples, so that the filter effect is good, and the stability of the whole system is not affected.
Disclosure of Invention
The present invention is directed to solving the above problems of the prior art. The current feedback type instrument amplifier with the high common mode rejection ratio enables the closed loop gain of the amplifier to be determined by the resistance ratio in a current feedback mode, eliminates the influence of the mismatch of the traditional three-operational amplifier structure and the resistance, and greatly improves the common mode rejection ratio of the amplifier. The technical scheme of the invention is as follows:
a low-noise chopper current feedback instrument amplification circuit, comprising: the device comprises a current feedback amplifying circuit (1) and a residual ripple filtering circuit (2), wherein the current feedback amplifying circuit (1) is used for collecting and amplifying a bioelectricity signal, the residual ripple filtering circuit (2) is used for filtering output ripples existing in an amplifier, and the signal output end of the current feedback amplifying circuit (1) is connected with the input end of the residual ripple filtering circuit (2);
the current feedback amplifying circuit (1) comprises a modulation chopper CH1, an input transconductance Gm1, a feedback transconductance Gm2, a modulation chopper CH2, a demodulation chopper CH3, a modulation chopper CH4, a cascode amplifier A1, a demodulation chopper CH5, an output amplifier A2, an input resistor Rin, an output resistor Ron, an output resistor Rop, a Miller compensation resistor Rmn, a Miller compensation resistor Rmp, a Miller compensation capacitor Cmn and a Miller compensation capacitor Cmp;
the residual ripple filtering circuit (2) comprises filtering resistors R1, R2, filtering capacitors C1, C2 and a filtering transconductance amplifier OTA;
two input ends of the modulation chopper CH1 are respectively connected with the positive end and the negative end of the external electrode; output terminal and input transconductance G of modulation chopper CH1M1Are connected to input transconductance GM1The output ends of the two-stage rectification and demodulation choppers are respectively connected with the input end of a demodulation chopper CH3 and the output end of a feedback transconductance Gm2, the output end of a demodulation chopper CH3 is connected with the input end of a modulation chopper CH4, the input end of a feedback transconductance Gm2 is connected with the output end of a modulation chopper CH2, the output end of a modulation chopper CH4 is connected with the input end of a cascode amplifier A1, the input end of a modulation chopper CH2 is connected with the two ends of an input resistor Ri, the output end of the cascode amplifier A1 is connected with the input end of a demodulation chopper CH5, the output end of a demodulation chopper CH5 is respectively connected with the input end of an output amplifier A2 and the input end of a Miller compensation resistor Rm, the output end of an output amplifier A2 is connected with the output end of a Miller compensation capacitor Cm, the two ends of an output resistor Ro and filter resistors R1 at the two ends of the input end of a residual ripple filtering circuit (2), and the output The output end of the filter resistor R2 is respectively connected with the input end of another filter capacitor C2 and the filterThe input end of the transconductance amplifier is connected, the output end of the filter capacitor C2 is connected to the ground, and the output end of the filter capacitor C1 is connected with the output end of the filter transconductance amplifier and serves as the output end of the whole circuit.
Further, the input transconductance Gm1 includes a PMOS transistor M1, a PMOS transistor M2, a PMOS transistor M5, and a PMOS transistor M6, wherein gates of the PMOS transistor M1 and the PMOS transistor M2 are respectively connected to an output terminal of the modulation chopper CH1 as differential input terminals, drains of the PMOS transistor M1 and the PMOS transistor M2 are respectively connected to a drain of the PMOS transistor M3 and a drain of the PMOS transistor M4 and two input terminals of the modulation chopper CH3, sources of the PMOS transistor M1 and the PMOS transistor M2 are connected to a drain of the PMOS transistor M6, a source of the PMOS transistor M6 is connected to a drain of the PMOS transistor M5, a source of the PMOS transistor M5 is connected to a power supply voltage VDD, and a gate of the PMOS transistor M5 and a gate of the PMOS transistor M6 are respectively connected to external signals VB1 and VB 2.
Further, the feedback transconductance Gm2 and the input transconductance Gm1 have the same structure, and the feedback transconductance Gm2 includes a PMOS transistor M3, a PMOS transistor M4, a PMOS transistor M7, and a PMOS transistor M8, wherein gates of the PMOS transistor M3 and the PMOS transistor M4 are respectively connected to an output terminal of the modulation chopper CH2 as differential feedback input terminals, drains of the PMOS transistor M3 and the PMOS transistor M4 are respectively connected to two input terminals of the modulation chopper CH3, sources of the PMOS transistor M3 and the PMOS transistor M4 are connected to a drain of the PMOS transistor M8, a source of the PMOS transistor M8 is connected to a drain of the PMOS transistor M7, a source of the PMOS transistor M7 is connected to a VDD voltage, and a gate of the PMOS transistor M7 and a gate of the PMOS transistor M8 are respectively connected to the external bias voltages VB1 and VB 2.
Further, the cascode amplifier a1 includes: PMOS transistor M9, PMOS transistor M10, PMOS transistor M11, PMOS transistor M12, PMOS transistor M21, PMOS transistor M22, PMOS transistor M23, NMOS transistor M13, NMOS transistor M14, NMOS transistor M15, NMOS transistor M16, NMOS transistor M24, NMOS transistor M25, resistor Rfn, resistor Rfp, capacitor Cfn, capacitor Cfp, wherein the sources of PMOS transistor M9 and PMOS transistor M11 are connected to the supply voltage VDD, the gates of PMOS transistor M9 and PMOS transistor M11 are connected together to the external bias voltage VB1, the drains of PMOS transistor M9 and PMOS transistor M11 are connected to the sources of PMOS transistor M10 and PMOS transistor M10, the gates of PMOS transistor M10 and PMOS transistor M10 are connected together to the external bias voltage VB 10, the drains of PMOS transistor M10 and PMOS transistor M10 are connected to the drains of PMOS transistor M10 and NMOS transistor M10, the drains of PMOS transistor M10 and NMOS transistor M10 are connected to the output terminal of NMOS transistor M10 and NMOS transistor M10, the output terminal of NMOS transistor M10 and NMOS transistor M10 are connected together, gates of the NMOS tubes M15 and M16 are connected to a drain of the NMOS tube M25, sources of the NMOS tubes M15 and M16 are connected to a ground voltage GND, a gate of the PMOS tube M21 is connected to an external bias voltage VB1, a source of the PMOS tube M21 is connected to a power supply voltage VDD, a drain of the PMOS tube M21 is connected to sources of the PMOS tubes M22 and M23, a gate of the PMOS tube M22 is externally connected to a bias voltage VCOM, a gate of the PMOS tube M23 is connected to one ends of a resistor Rfn, a resistor Rfp, a capacitor Cfn and a capacitor Cfp, another ends of a resistor Rfn and a capacitor Cfn are connected to a drain of the NMOS tube M17 and a drain of the NMOS 19, another ends of the resistor Rfp and the capacitor Cfp are connected to a drain of the M18 and a drain of the NMOS tube M20, drains of the PMOS tubes M22 and M22 are connected to a drain of the NMOS tubes M24, a drain of the NMOS tubes M24 and a source of the NMOS tubes 24 and a gate of the NMOS tubes 24 are connected to a ground voltage GND.
Further, the output amplifier a2 includes: the transistor comprises a PMOS tube M17, a PMOS tube M18, an NMOS tube M19, an NMOS tube M20, a resistor Rmn, a resistor Rmp, a resistor Ron, a resistor Rop, a resistor Ri, a capacitor Cmn and a capacitor Cmp, wherein sources of the PMOS tube M17 and the PMOS tube M18 are connected to a power supply voltage VDD, gates of the PMOS tube M17 and the PMOS tube M18 are connected to an external bias voltage VB3, drains of the PMOS tube M17 and the PMOS tube M18 are connected with one end of the resistor Ron and one end of the resistor Rop and drains of the NMOS tube M19 and the NMOS tube M20 respectively, gates of the NMOS tube M19 and the NMOS tube M20 are connected to one ends of the resistor Rmn and the resistor Rmp respectively, the other ends of the resistor Rmn and the resistor Rmp are connected with one ends of the capacitor Cmn and the capacitor Cmp, the other ends of the capacitor Cmn and the capacitor Cmp are connected to drains of the PMOS tube M17 and the NMOS tube M18 respectively, and a source of the NMOS tube M19.
Further, the filtering transconductance amplifier buffer of the residual ripple filtering circuit (2) comprises: a PMOS tube M26, a PMOS tube M27, a PMOS tube M28, a PMOS tube M29, a PMOS tube M30, a PMOS tube M31, an NMOS tube M31, a resistor Rn 31, a resistor Rp 31, a resistor Rcn, a resistor Rcp, a capacitor 31, a capacitor Ccp, a capacitor Cn 31, a capacitor Cp 31, a capacitor Cn 31, and a capacitor Cp 31, wherein one end of the resistor Rn 31 and the resistor Rp 31 is connected to an output end of the current feedback amplifying circuit, namely the PMOS tube M31 and the resistor Rp 31 are connected to a common drain terminal of the PMOS tube M31, the NMOS tube M31 and the drain terminal Cn 31 of the NMOS tube M31, the resistor Rn 31 and the resistor Rn 31 are connected to a common drain terminal of the PMOS tube M31, the resistor Rn 31 and the drain terminal of the PMOS tube Cn 31, the drain terminal of the PMOS tube Cn 31 and the drain terminal of the drain terminal Cn 31 are connected to the resistor Cn 31, the PMOS tube 31, the resistor Rn 31, the drain terminal of the PMOS tube 31, the drain, as the input end of the transconductance amplifier, the other end of the capacitor Cn2 and the capacitor Cp2 is connected to a ground voltage GND, the drains of the PMOS transistor M26 and the PMOS transistor M29 are respectively connected to the drains of the NMOS transistor M32 and the NMOS transistor M35 and one end of the resistor Rcn and the resistor Rcp, the sources of the PMOS transistor M26 and the PMOS transistor M26 are respectively connected to the sources of the PMOS transistor M26 and are respectively connected to the drains of the PMOS transistor M26 and the PMOS transistor M26, the gates of the PMOS transistor M26 and the PMOS transistor M26 are commonly connected to an external bias voltage VB 26, the sources of the PMOS transistor M26 and the PMOS transistor M26 are connected to a power supply voltage VDD, the gates of the PMOS transistor M26 and the PMOS transistor M26 are respectively connected to the common drain terminal of the PMOS transistor M26 and the NMOS transistor M26, the output end of the capacitor cc 26 and the drain of the capacitor Cp 26, the drain of the PMOS transistor M26 and the drain of the resistor Rcp are respectively connected to the drain of the PMOS transistor M26 and the drain of the NMOS transistor M26, the drain of the resistor Rcp, the drain of the PMOS transistor M26 and the drain of the PMOS transistor M26 are respectively connected to the drain of the NMOS transistor M36 The sources of the NMOS transistor M33 and the NMOS transistor M34 are directly connected to the gates of the NMOS transistor M32 and the NMOS transistor M35, the sources of the NMOS transistor M32, the NMOS transistor M33, the NMOS transistor M34 and the NMOS transistor M35 are commonly connected to a ground voltage GND, the gates of the PMOS transistor M36 and the PMOS transistor M37 are connected to an external bias VB1, the sources of the PMOS transistor M36 and the PMOS transistor M37 are connected to a power supply voltage VDD, and the gates of the NMOS transistor M32 and the NMOS transistor M32 are connected to the ground voltage GND with one end of a resistor Rcn and a resistor Rcp and the sources of the NMOS transistor M32 and the NMOS transistor M35 are connected to the sources of the NMOS transistor M32 and the NMOS transistor M35.
Furthermore, in the current feedback amplifying circuit (1), the feedback transconductance Gm2 and the input transconductance Gm1 have the same structure, the gates of the PMOS transistor M5 and the PMOS transistor M7 and the gates of the PMOS transistor M6 and the PMOS transistor M8 are respectively connected to external bias voltages VB1 and VB2, the current flowing through the feedback transconductance Gm2 is equal to the current flowing through the input transconductance Gm1, the drains of the PMOS transistor M1 and the PMOS transistor M3 and the drains of the PMOS transistor M2 and the PMOS transistor M4 are connected in pairs, and are connected to the input end of the cascode amplifier A1 through the two ends of the chopper, after the input transconductance Gm1 and the feedback transconductance Gm2 convert the corresponding input voltage and feedback voltage into input current and feedback current respectively, the difference in current between the two at the phases is taken care of by the high gain cascode amplifier a1, ensuring that the two are exactly matched, since two ends of the input electrode of the feedback transconductance Gm2 are respectively connected to two ends of the resistor Ri, the current of the two ends of the feedback transconductance Gm2 is equal to that of the input transconductance Gm 1; the two-terminal current, therefore, the closed-loop gain of the current feedback amplifying circuit has:in the formula VinFor inputting differential signals, RiIs the resistance value of the resistor Ri, RonIs the resistance value of the resistor Ron, RopIs the resistance of the resistor Rop.
Further, the structure adopted by the residual ripple filtering circuit (2) is a second-order Sallen-Key filtering structure, wherein the gates of a PMOS transistor M27 and a PMOS transistor M28 in the transconductance amplifier are respectively connected with two output terminals Von and Vop formed by the common drain terminals of a PMOS transistor M36 and an NMOS transistor M38 and the common drain terminals of a PMOS transistor M37 and an NMOS transistor M39 to form a full differential single gain buffer, and a resistor Rn1, a resistor Rp1, a resistor Rn2, a resistor Rp2, a capacitor Cn1, a capacitor Cp1, a capacitor Cn2 and a capacitor Cp2 form a filtering capacitor and a filtering resistor of the whole second-order filtering circuit, so that the transfer function of the second-order filtering circuit is obtained as follows:wherein,fc is the cut-off frequency of the filter circuit, Q is the quality factor of the filter circuit, Rn1Is the resistance value, R, of the resistor Rn1n2Is the resistance value, C, of the resistor Rn2n1Is the capacitance value, C, of the capacitance Cn1n2The cut-off frequency of the filter is adjusted by adjusting the resistance value and the capacitance value of the capacitor Cn2, so as to better filter out the ripple.
The invention has the following advantages and beneficial effects:
the invention provides a low-noise chopping current feedback instrument amplifying circuit, which is a current feedback mode, so that the closed-loop gain of an amplifier is determined by a resistor ratio, the influence of the mismatch of a traditional three-operational amplifier structure and a resistor is eliminated, the common-mode rejection ratio of the amplifier is greatly improved, meanwhile, the two-stage chopping structure is used, the interference of 1/f noise is greatly eliminated, and the low-noise chopping current feedback instrument amplifying circuit comprises a current feedback amplifying circuit and a residual ripple wave filter circuit. The current feedback amplifying circuit is composed of a modulation chopper CH1, an input transconductance Gm1, a feedback transconductance Gm2, a modulation chopper CH2, a demodulation chopper CH3, a modulation chopper CH4, a cascode amplifier A1, a demodulation chopper CH5, an output amplifier A2, an input resistor Rin, an output resistor Ro, a Miller compensation resistor Rm and a Miller compensation capacitor Cm, and the residual ripple filtering circuit is composed of filter resistors R1 and R2, filter capacitors C1 and C2 and a filter transconductance amplifier. The output ripple amplitude caused by chopping is effectively reduced through the designed residual noise filter circuit, and the accuracy of the whole circuit is optimized. Therefore, the instrument amplifying circuit with the advantages of high common mode rejection ratio and low noise is obtained.
The micro-current low-voltage chopper type current feedback instrument amplifying circuit can realize measurement and collection of bioelectricity signals such as electrocardiosignals, myoelectricity signals and the like, and has the following beneficial effects.
Firstly, the circuit structure is suitable for low-voltage system work, MOS tubes in the whole circuit work in a sub-threshold region, and the MOS tubes are used as an important ring of a portable medical system and have lower power consumption.
Secondly, the circuit can realize a measurement result with higher precision, has a common mode rejection ratio larger than 100dB and a gain of 40dB, and simultaneously avoids signal distortion.
And thirdly, the circuit adopts a three-stage amplification structure, has higher gain and provides higher precision for the whole current negative feedback structure. Meanwhile, the input transconductance is improved, the input reference noise is reduced, and the noise and offset are further reduced by adopting a two-stage chopping structure, so that better noise performance is achieved.
Fourth, the high frequency output ripple at the first harmonic is reduced 1/43 using a second order Sallen-Key low pass filter. The ripple is greatly restrained, and the precision of the output signal is further improved.
And fifthly, the resistor is used as a feedback network, so that the whole circuit area is reduced. And relatively good system precision is realized through good matching.
Drawings
FIG. 1 is a typical application scenario of the present invention providing a preferred embodiment instrumentation amplifier:
fig. 2 is a circuit diagram of a conventional three-op-amp instrumentation amplifier:
fig. 3 is a schematic block diagram of an amplifying circuit of a low-noise chopper current feedback instrument according to a preferred embodiment of the present invention:
fig. 4 is a circuit diagram of a current feedback amplifying circuit according to a preferred embodiment of the present invention:
fig. 5 is a circuit diagram of a residual ripple filtering circuit according to a preferred embodiment of the present invention:
fig. 6 is a circuit gain simulation graph of an amplifying circuit of a low-noise chopper current feedback instrument according to a preferred embodiment of the present invention:
fig. 7 is a simulation graph of the common mode rejection ratio of the low-noise chopper current feedback instrument amplifying circuit according to the preferred embodiment of the present invention:
fig. 8 is a simulation graph of input reference noise of an amplifying circuit of a low-noise chopper current feedback instrument according to a preferred embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described in detail and clearly with reference to the accompanying drawings. The described embodiments are only some of the embodiments of the present invention.
The technical scheme for solving the technical problems is as follows:
the low-noise chopping current feedback instrument amplifying circuit in the embodiment of the application comprises a current feedback amplifying circuit and a residual ripple wave filtering circuit. The current feedback amplifying circuit is composed of a modulation chopper CH1, an input transconductance Gm1, a feedback transconductance Gm2, a modulation chopper CH2, a demodulation chopper CH3, a modulation chopper CH4, a cascode amplifier A1, a demodulation chopper CH5, an output amplifier A2, an input resistor Rin, an output resistor Ro, a Miller compensation resistor Rm and a Miller compensation capacitor Cm, and the residual ripple filtering circuit is composed of filter resistors R1 and R2, filter capacitors C1 and C2 and a filter transconductance amplifier. According to the invention, the input amplifying circuit and the current feedback loop are combined to form a current feedback structure, so that good common mode rejection performance is realized, 1/f noise is effectively reduced through a two-stage chopping structure, the output ripple amplitude caused by chopping is effectively reduced through a designed residual noise filter circuit, and the overall circuit precision is optimized, thereby realizing the low-noise chopping current feedback type instrument amplifying circuit.
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and specific implementation methods.
Examples
As a preferred solution, a low noise chopper current feedback instrument amplifier circuit, as shown in figure 2,
a low-noise chopping current feedback instrument amplifying circuit comprises a current feedback amplifying circuit (1) and a residual ripple filtering circuit (2).
Two input ends of the low-noise chopping current feedback instrument amplifying circuit are respectively connected with the positive end and the negative end of the external electrode; and is connected with the input end of a modulation chopper CH1, the output end of a modulation chopper CH1 is connected with the input end of an input transconductance Gm1, and the output end of the input transconductance Gm1 is respectively connected with the input end of a demodulation chopper CH3 and the output end of a feedback transconductance Gm 2. The output end of the demodulation chopper CH3 is connected with the input end of the modulation chopper CH4, the input end of the feedback transconductance Gm2 is connected with the output end of the modulation chopper CH2, the output end of the modulation chopper CH4 is connected with the input end of the cascode amplifier A1, the input end of the modulation chopper CH2 is connected with two ends of an input resistor Ri, the output end of the cascode amplifier A1 is connected with the input end of the demodulation chopper CH5, and the output end of the demodulation chopper CH5 is connected with the input end of the output amplifier A2 and the input end of the Miller compensation resistor Rm respectively. The output end of the output amplifier a2 is connected to the output end of the miller compensation capacitor Cm, the two ends of the output resistor Ro and the filter resistors R1 at the two ends of the input end of the residual ripple filtering circuit (2), the output end of the filter resistor R1 at the input end of the residual ripple filtering circuit is connected to the input end of another filter resistor R2 and the input end of the filter capacitor C1, the output end of the filter resistor R2 is connected to the input end of another filter capacitor C2 and the input end of the filter transconductance amplifier, the output end of the filter capacitor C2 is connected to the ground, and the output end of the filter capacitor C1 is connected to the output end of the filter transconductance amplifier and serves as the output end of the whole circuit.
As a preferred technical solution, as shown in fig. 2, the current feedback amplifying circuit (1) includes a modulation chopper CH1, an input transconductance Gm1, a feedback transconductance Gm2, a modulation chopper CH2, a demodulation chopper CH3, a modulation chopper CH4, a cascode amplifier a1, a demodulation chopper CH5, an output amplifier a2, an input resistor Rin, an output resistor Ro, a miller compensation resistor Rm, and a miller compensation capacitor Cm; two input ends of the current feedback amplifying circuit are respectively connected with the positive end and the negative end of the external electrode to serve as input ends of the whole circuit structure and are connected with the input end of the modulation chopper CH1, the output end of the modulation chopper CH1 is connected with the input end of the input transconductance Gm1, and the output end of the input transconductance Gm1 is respectively connected with the input end of the demodulation chopper CH3 and the output end of the feedback transconductance Gm 2. The output end of the demodulation chopper CH3 is connected with the input end of the modulation chopper CH4, the input end of the feedback transconductance Gm2 is connected with the output end of the modulation chopper CH2, the output end of the modulation chopper CH4 is connected with the input end of the cascode amplifier A1, the input end of the modulation chopper CH2 is connected with two ends of an input resistor Ri, the output end of the cascode amplifier A1 is connected with the input end of the demodulation chopper CH5, and the output end of the demodulation chopper CH5 is connected with the input end of the output amplifier A2 and the input end of the Miller compensation resistor Rm respectively. The output end of the output amplifier a2 is connected to the output end of the miller compensation capacitor Cm and the two ends of the output resistor Ro, and is used as the output end of the current feedback amplifying circuit.
The input transconductance Gm1 comprises a PMOS tube M1, a PMOS tube M2, a PMOS tube M5 and a PMOS tube M6, wherein gates of the PMOS tube M1 and the PMOS tube M2 are respectively used as differential input ends and connected with an output end of a modulation chopper CH1, drains of the PMOS tube M1 and the PMOS tube M2 are respectively connected with a drain of the PMOS tube M3 and a drain of the PMOS tube M4 and two input ends of the modulation chopper CH3, sources of the PMOS tube M1 and the PMOS tube M2 are connected with a drain of the PMOS tube M6, a source of the PMOS tube M6 is connected with a drain of the PMOS tube M5, a source of the PMOS tube M5 is connected with a power supply voltage VDD, and a gate of the PMOS tube M5 and a gate of the PMOS tube M6 are respectively connected with external signals VB1 and VB 2.
The feedback transconductance Gm2 and the input transconductance Gm1 have the same structure, the feedback transconductance Gm2 comprises a PMOS tube M3, a PMOS tube M4, a PMOS tube M7 and a PMOS tube M8, wherein gates of the PMOS tube M3 and the PMOS tube M4 are respectively used as differential feedback input end terminals to be connected with an output end of the modulation chopper CH2, drains of the PMOS tube M3 and the PMOS tube M4 are respectively connected to two input ends of the modulation chopper CH3, sources of the PMOS tube M3 and the PMOS tube M4 are connected to a drain of the PMOS tube M8, a source of the PMOS tube M8 is connected with a drain of the PMOS tube M7, a source of the PMOS tube M7 is connected to a power supply voltage VDD, and a gate of the PMOS tube M7 and a gate of the PMOS tube M8 are respectively connected to external bias voltages VB1 and VB 2.
The cascode amplifier A1 comprises: PMOS transistor M9, PMOS transistor M10, PMOS transistor M11, PMOS transistor M12, PMOS transistor M21, PMOS transistor M22, PMOS transistor M23, NMOS transistor M13, NMOS transistor M14, NMOS transistor M15, NMOS transistor M16, NMOS transistor M24, NMOS transistor M25, resistor Rfn, resistor Rfp, capacitor Cfn, capacitor Cfp, wherein the sources of PMOS transistor M9 and PMOS transistor M11 are connected to the supply voltage VDD, the gates of PMOS transistor M9 and PMOS transistor M11 are connected together to the external bias voltage VB1, the drains of PMOS transistor M9 and PMOS transistor M11 are connected to the sources of PMOS transistor M10 and PMOS transistor M10, the gates of PMOS transistor M10 and PMOS transistor M10 are connected together to the external bias voltage VB 10, the drains of PMOS transistor M10 and PMOS transistor M10 are connected to the drains of PMOS transistor M10 and NMOS transistor M10, the drains of PMOS transistor M10 and NMOS transistor M10 are connected to the output terminal of NMOS transistor M10 and NMOS transistor M10, the output terminal of NMOS transistor M10 and NMOS transistor M10 are connected together, gates of the NMOS tubes M15 and M16 are connected to a drain of the NMOS tube M25, sources of the NMOS tubes M15 and M16 are connected to a ground voltage GND, a gate of the PMOS tube M21 is connected to an external bias voltage VB1, a source of the PMOS tube M21 is connected to a power supply voltage VDD, a drain of the PMOS tube M21 is connected to sources of the PMOS tubes M22 and M23, a gate of the PMOS tube M22 is externally connected to a bias voltage VCOM, a gate of the PMOS tube M23 is connected to one ends of a resistor Rfn, a resistor Rfp, a capacitor Cfn and a capacitor Cfp, another ends of a resistor Rfn and a capacitor Cfn are connected to a drain of the NMOS tube M17 and a drain of the NMOS 19, another ends of the resistor Rfp and the capacitor Cfp are connected to a drain of the M18 and a drain of the NMOS tube M20, drains of the PMOS tubes M22 and M22 are connected to a drain of the NMOS tubes M24, a drain of the NMOS tubes M24 and a source of the NMOS tubes 24 and a gate of the NMOS tubes 24 are connected to a ground voltage GND.
The output amplifier A2 comprises: the transistor comprises a PMOS tube M17, a PMOS tube M18, an NMOS tube M19, an NMOS tube M20, a resistor Rmn, a resistor Rmp, a resistor Ron, a resistor Rop, a resistor Ri, a capacitor Cmn and a capacitor Cmp, wherein the sources of the PMOS tube M17 and the PMOS tube M18 are connected to a power supply voltage VDD, the gates of the PMOS tube M17 and the PMOS tube M18 are connected to an external bias voltage VB3, the drains of the PMOS tube M17 and the PMOS tube M18 are connected with the resistor Ron, one end of the resistor Rop and the drains of the NMOS tube M19 and the NMOS tube M20 respectively, the gates of the NMOS tube M19 and the NMOS tube M20 are connected to one ends of the resistor Rmn and the resistor Rmp respectively, the other ends of the resistor Rmn and the resistor Rmp are connected with one ends of the capacitor Cmn and the capacitor Cmp, the other ends of the capacitor Cmn and the capacitor Cmp are connected to the drains of the PMOS tube M17 and the NMOS tube M18 respectively, and the source of the NMOS tube.
The residual ripple filtering circuit (2) comprises: a PMOS tube M26, a PMOS tube M27, a PMOS tube M28, a PMOS tube M29, a PMOS tube M30, a PMOS tube M31, an NMOS tube M31, a resistor Rn 31, a resistor Rp 31, a resistor Rcn, a resistor Rcp, a capacitor 31, a capacitor Ccp, a capacitor Cn 31, a capacitor Cp 31, a capacitor Cn 31, and a capacitor Cp 31, wherein one end of the resistor Rn 31 and the resistor Rp 31 is connected to an output end of the current feedback amplifying circuit, namely the PMOS tube M31 and the resistor Rp 31 are connected to a common drain terminal of the PMOS tube M31, the NMOS tube M31 and the drain terminal Cn 31 of the NMOS tube M31, the resistor Rn 31 and the resistor Rn 31 are connected to a common drain terminal of the PMOS tube M31, the resistor Rn 31 and the drain terminal of the PMOS tube Cn 31, the drain terminal of the PMOS tube Cn 31 and the drain terminal of the drain terminal Cn 31 are connected to the resistor Cn 31, the PMOS tube 31, the resistor Rn 31, the drain terminal of the PMOS tube 31, the drain, as the input end of the transconductance amplifier, the other end of the capacitor Cn2 and the capacitor Cp2 is connected to a ground voltage GND, the drains of the PMOS transistor M26 and the PMOS transistor M29 are respectively connected to the drains of the NMOS transistor M32 and the NMOS transistor M35 and one end of the resistor Rcn and the resistor Rcp, the sources of the PMOS transistor M26 and the PMOS transistor M26 are respectively connected to the sources of the PMOS transistor M26 and are respectively connected to the drains of the PMOS transistor M26 and the PMOS transistor M26, the gates of the PMOS transistor M26 and the PMOS transistor M26 are commonly connected to an external bias voltage VB 26, the sources of the PMOS transistor M26 and the PMOS transistor M26 are connected to a power supply voltage VDD, the gates of the PMOS transistor M26 and the PMOS transistor M26 are respectively connected to the common drain terminal of the PMOS transistor M26 and the NMOS transistor M26, the output end of the capacitor cc 26 and the drain of the capacitor Cp 26, the drain of the PMOS transistor M26 and the drain of the resistor Rcp are respectively connected to the drain of the PMOS transistor M26 and the drain of the NMOS transistor M26, the drain of the resistor Rcp, the drain of the PMOS transistor M26 and the drain of the PMOS transistor M26 are respectively connected to the drain of the NMOS transistor M36 The sources of the NMOS transistor M33 and the NMOS transistor M34 are directly connected to the gates of the NMOS transistor M32 and the NMOS transistor M35, the sources of the NMOS transistor M32, the NMOS transistor M33, the NMOS transistor M34 and the NMOS transistor M35 are commonly connected to a ground voltage GND, the gates of the PMOS transistor M36 and the PMOS transistor M37 are connected to an external bias VB1, the sources of the PMOS transistor M36 and the PMOS transistor M37 are connected to a power supply voltage VDD, and the gates of the NMOS transistor M32 and the NMOS transistor M32 are connected to the ground voltage GND with one end of a resistor Rcn and a resistor Rcp and the sources of the NMOS transistor M32 and the NMOS transistor M35 are connected to the sources of the NMOS transistor M32 and the NMOS transistor M35.
In the current feedback amplifying circuit (1), the feedback transconductance Gm2 and the input transconductance Gm1 have the same structure, the gates of the PMOS transistor M5 and the PMOS transistor M7 and the gates of the PMOS transistor M6 and the PMOS transistor M8 are respectively connected to an external bias voltage VB1 and VB2, so that the currents flowing through the feedback transconductance Gm2 and the input transconductance Gm1 are equal, the drains of the PMOS transistor M1 and the PMOS transistor M3 and the drains of the PMOS transistor M2 and the PMOS transistor M4 are connected in pairs and are connected to the input end of the cascode amplifier a1 through two ends of a chopper, and after the input transconductance Gm1 and the feedback transconductance Gm2 convert the corresponding input voltage and the feedback voltage into the input current and the feedback current respectively, the high-gain cascode amplifier a1 is responsible for the difference of the currents at the two phases, thereby ensuring the accurate matching between the input transconductance Gm1 and the feedback transconductance Gm 2. Due to feedback transconductance Gm2Two ends of the input pole are respectively connected to two ends of the resistor Ri, and the current at two ends of the feedback transconductance Gm2 is equal to that of the input transconductance Gm 1; the two-terminal current, therefore, the closed-loop gain of the current feedback amplifying circuit has:in the formula VinFor inputting differential signals, RiIs the resistance value of the resistor Ri, RonIs the resistance value of the resistor Ron, RopIs the resistance of the resistor Rop.
The structure adopted by the residual ripple filtering circuit (2) is a second-order Sallen-Key filtering structure, wherein the grids of a PMOS tube M27 and a PMOS tube M28 in the transconductance amplifier are respectively connected with two output ends Von and Vop formed by the common drain ends of a PMOS tube M36 and an NMOS tube M38 and the common drain ends of the PMOS tube M37 and an NMOS tube M39 to form a full differential single-gain buffer, a resistor Rn1, a resistor Rp1, a resistor Rn2, a resistor Rp2, a capacitor Cn1, a capacitor Cp1, a capacitor Cn2 and a capacitor Cp2 form a filtering capacitor and a filtering resistor of the whole second-order filtering circuit, and the transfer function of the obtained second-order filtering circuit is as follows:wherein,fc is the cut-off frequency of the filter circuit, Q is the quality factor of the filter circuit, Rn1Is the resistance value, R, of the resistor Rn1n2Is the resistance value, C, of the resistor Rn2n1Is the capacitance value, C, of the capacitance Cn1n2The cut-off frequency of the filter can be adjusted by adjusting the resistance value and the capacitance value of the capacitor Cn2, so as to better filter out the ripple.
The above examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure. After reading the description of the invention, the skilled person can make various changes or modifications to the invention, and these equivalent changes and modifications also fall into the scope of the invention defined by the claims.

Claims (8)

1. A low-noise chopper current feedback instrument amplifying circuit is characterized by comprising: the device comprises a current feedback amplifying circuit (1) and a residual ripple filtering circuit (2), wherein the current feedback amplifying circuit (1) is used for collecting and amplifying a bioelectricity signal, the residual ripple filtering circuit (2) is used for filtering output ripples existing in an amplifier, and the signal output end of the current feedback amplifying circuit (1) is connected with the input end of the residual ripple filtering circuit (2);
the current feedback amplifying circuit (1) comprises a modulation chopper CH1, an input transconductance Gm1, a feedback transconductance Gm2, a modulation chopper CH2, a demodulation chopper CH3, a modulation chopper CH4 cascode amplifier A1, a demodulation chopper CH5, an output amplifier A2, an input resistor Rin, an output resistor Ron, an output resistor Rop, a Miller compensation resistor Rmn, a Miller compensation resistor Rmp, a Miller compensation capacitor Cmn and a Miller compensation capacitor Cmp;
the residual ripple filtering circuit (2) comprises filtering resistors R1, R2, filtering capacitors C1, C2 and a filtering transconductance amplifier OTA;
two input ends of the modulation chopper CH1 are respectively connected with the positive end and the negative end of the external electrode; output terminal and input transconductance G of modulation chopper CH1M1Are connected to input transconductance GM1The output ends of the two-stage rectification and demodulation choppers are respectively connected with the input end of a demodulation chopper CH3 and the output end of a feedback transconductance Gm2, the output end of a demodulation chopper CH3 is connected with the input end of a modulation chopper CH4, the input end of a feedback transconductance Gm2 is connected with the output end of a modulation chopper CH2, the output end of a modulation chopper CH4 is connected with the input end of a cascode amplifier A1, the input end of a modulation chopper CH2 is connected with the two ends of an input resistor Ri, the output end of the cascode amplifier A1 is connected with the input end of a demodulation chopper CH5, the output end of a demodulation chopper CH5 is respectively connected with the input end of an output amplifier A2 and the input end of a Miller compensation resistor Rm, the output end of an output amplifier A2 is connected with the output end of a Miller compensation capacitor Cm, the two ends of an output resistor Ro and filter resistors R1 at the two ends of the input end of a residual ripple filtering circuit (2), and the output The output end of the filter resistor R2 is respectively connected with the input end of another filter capacitor C2 and the input end of the filter transconductance amplifier, the output end of the filter capacitor C2 is connected to the ground, and the output end of the filter capacitor C1 is connected with the output end of the filter transconductance amplifier and serves as the output end of the whole circuit.
2. The low-noise chopper current feedback instrument amplifying circuit as claimed in claim 1, wherein the input transconductance Gm1 includes a PMOS transistor M1, a PMOS transistor M2, a PMOS transistor M5, and a PMOS transistor M6, wherein gates of the PMOS transistor M1 and a PMOS transistor M2 are respectively connected as differential inputs to an output terminal of the modulation chopper CH1, drains of the PMOS transistor M1 and a PMOS transistor M2 are respectively connected to a drain of the PMOS transistor M3 and a drain of the PMOS transistor M4, and two input terminals of the modulation chopper CH3, sources of the PMOS transistor M1 and a PMOS transistor M2 are connected to a drain of the PMOS transistor M6, a source of the PMOS transistor M6 is connected to a drain of the PMOS transistor M5, a source of the PMOS transistor M5 is connected to a power supply voltage VDD, and gates of the PMOS transistor M5 and a PMOS transistor M6 are respectively connected to external signals VB1 and VB 2.
3. The low-noise chopper current feedback instrument amplifying circuit as claimed in claim 2, wherein the feedback transconductance Gm2 has the same structure as the input transconductance Gm1, the feedback transconductance Gm2 includes a PMOS transistor M3, a PMOS transistor M4, a PMOS transistor M7 and a PMOS transistor M8, wherein gates of the PMOS transistor M3 and the PMOS transistor M4 are respectively connected to an output terminal of the modulation chopper CH2 as differential feedback input terminals, drains of the PMOS transistor M3 and the PMOS transistor M4 are respectively connected to two input terminals of the modulation chopper CH3, sources of the PMOS transistor M3 and the PMOS transistor M4 are connected to a drain of the PMOS transistor M8, a source of the PMOS transistor M8 is connected to a drain of the PMOS transistor M7, a source of the PMOS transistor M7 is connected to the power supply voltage VDD, and a gate of the PMOS transistor M7 and a gate of the PMOS transistor M8 are respectively connected to the external bias voltages VB1 and VB 2.
4. A low noise chopped current feedback instrument amplifier circuit as defined in any one of claims 1-3 in which said cascode amplifier a1 includes: PMOS transistor M9, PMOS transistor M10, PMOS transistor M11, PMOS transistor M12, PMOS transistor M21, PMOS transistor M22, PMOS transistor M23, NMOS transistor M13, NMOS transistor M14, NMOS transistor M15, NMOS transistor M16, NMOS transistor M24, NMOS transistor M25, resistor Rfn, resistor Rfp, capacitor Cfn, capacitor Cfp, wherein the sources of PMOS transistor M9 and PMOS transistor M11 are connected to the supply voltage VDD, the gates of PMOS transistor M9 and PMOS transistor M11 are connected together to the external bias voltage VB1, the drains of PMOS transistor M9 and PMOS transistor M11 are connected to the sources of PMOS transistor M10 and PMOS transistor M10, the gates of PMOS transistor M10 and PMOS transistor M10 are connected together to the external bias voltage VB 10, the drains of PMOS transistor M10 and PMOS transistor M10 are connected to the drains of PMOS transistor M10 and NMOS transistor M10, the drains of PMOS transistor M10 and NMOS transistor M10 are connected to the output terminal of NMOS transistor M10 and NMOS transistor M10, the output terminal of NMOS transistor M10 and NMOS transistor M10 are connected together, gates of the NMOS tubes M15 and M16 are connected to a drain of the NMOS tube M25, sources of the NMOS tubes M15 and M16 are connected to a ground voltage GND, a gate of the PMOS tube M21 is connected to an external bias voltage VB1, a source of the PMOS tube M21 is connected to a power supply voltage VDD, a drain of the PMOS tube M21 is connected to sources of the PMOS tubes M22 and M23, a gate of the PMOS tube M22 is externally connected to a bias voltage VCOM, a gate of the PMOS tube M23 is connected to one ends of a resistor Rfn, a resistor Rfp, a capacitor Cfn and a capacitor Cfp, another ends of a resistor Rfn and a capacitor Cfn are connected to a drain of the NMOS tube M17 and a drain of the NMOS 19, another ends of the resistor Rfp and the capacitor Cfp are connected to a drain of the M18 and a drain of the NMOS tube M20, drains of the PMOS tubes M22 and M22 are connected to a drain of the NMOS tubes M24, a drain of the NMOS tubes M24 and a source of the NMOS tubes 24 and a gate of the NMOS tubes 24 are connected to a ground voltage GND.
5. A low noise chopped current feedback instrument amplifier circuit as defined in any one of claims 1-3 in which said output amplifier a2 includes: the transistor comprises a PMOS tube M17, a PMOS tube M18, an NMOS tube M19, an NMOS tube M20, a resistor Rmn, a resistor Rmp, a resistor Ron, a resistor Rop, a resistor Ri, a capacitor Cmn and a capacitor Cmp, wherein sources of the PMOS tube M17 and the PMOS tube M18 are connected to a power supply voltage VDD, gates of the PMOS tube M17 and the PMOS tube M18 are connected to an external bias voltage VB3, drains of the PMOS tube M17 and the PMOS tube M18 are connected with one end of the resistor Ron and one end of the resistor Rop and drains of the NMOS tube M19 and the NMOS tube M20 respectively, gates of the NMOS tube M19 and the NMOS tube M20 are connected to one ends of the resistor Rmn and the resistor Rmp respectively, the other ends of the resistor Rmn and the resistor Rmp are connected with one ends of the capacitor Cmn and the capacitor Cmp, the other ends of the capacitor Cmn and the capacitor Cmp are connected to drains of the PMOS tube M17 and the NMOS tube M18 respectively, and a source of the NMOS tube M19.
6. A low-noise chopped current feedback instrument amplifier circuit according to any one of claims 1-3, characterized in that the filtering transconductance amplifier buffer stage of said residual ripple filtering circuit (2) comprises: a PMOS tube M26, a PMOS tube M27, a PMOS tube M28, a PMOS tube M29, a PMOS tube M30, a PMOS tube M31, an NMOS tube M31, a resistor Rn 31, a resistor Rp 31, a resistor Rcn, a resistor Rcp, a capacitor 31, a capacitor Ccp, a capacitor Cn 31, a capacitor Cp 31, a capacitor Cn 31, and a capacitor Cp 31, wherein one end of the resistor Rn 31 and the resistor Rp 31 is connected to an output end of the current feedback amplifying circuit, namely the PMOS tube M31 and the resistor Rp 31 are connected to a common drain terminal of the PMOS tube M31, the NMOS tube M31 and the drain terminal Cn 31 of the NMOS tube M31, the resistor Rn 31 and the resistor Rn 31 are connected to a common drain terminal of the PMOS tube M31, the resistor Rn 31 and the drain terminal of the PMOS tube Cn 31, the drain terminal of the PMOS tube Cn 31 and the drain terminal of the drain terminal Cn 31 are connected to the resistor Cn 31, the PMOS tube 31, the resistor Rn 31, the drain terminal of the PMOS tube 31, the drain, as the input end of the transconductance amplifier, the other end of the capacitor Cn2 and the capacitor Cp2 is connected to a ground voltage GND, the drains of the PMOS transistor M26 and the PMOS transistor M29 are respectively connected to the drains of the NMOS transistor M32 and the NMOS transistor M35 and one end of the resistor Rcn and the resistor Rcp, the sources of the PMOS transistor M26 and the PMOS transistor M26 are respectively connected to the sources of the PMOS transistor M26 and are respectively connected to the drains of the PMOS transistor M26 and the PMOS transistor M26, the gates of the PMOS transistor M26 and the PMOS transistor M26 are commonly connected to an external bias voltage VB 26, the sources of the PMOS transistor M26 and the PMOS transistor M26 are connected to a power supply voltage VDD, the gates of the PMOS transistor M26 and the PMOS transistor M26 are respectively connected to the common drain terminal of the PMOS transistor M26 and the NMOS transistor M26, the output end of the capacitor cc 26 and the drain of the capacitor Cp 26, the drain of the PMOS transistor M26 and the drain of the resistor Rcp are respectively connected to the drain of the PMOS transistor M26 and the drain of the NMOS transistor M26, the drain of the resistor Rcp, the drain of the PMOS transistor M26 and the drain of the PMOS transistor M26 are respectively connected to the drain of the NMOS transistor M36 The sources of the NMOS transistor M33 and the NMOS transistor M34 are directly connected to the gates of the NMOS transistor M32 and the NMOS transistor M35, the sources of the NMOS transistor M32, the NMOS transistor M33, the NMOS transistor M34 and the NMOS transistor M35 are commonly connected to a ground voltage GND, the gates of the PMOS transistor M36 and the PMOS transistor M37 are connected to an external bias VB1, the sources of the PMOS transistor M36 and the PMOS transistor M37 are connected to a power supply voltage VDD, and the gates of the NMOS transistor M32 and the NMOS transistor M32 are connected to the ground voltage GND with one end of a resistor Rcn and a resistor Rcp and the sources of the NMOS transistor M32 and the NMOS transistor M35 are connected to the sources of the NMOS transistor M32 and the NMOS transistor M35.
7. The low-noise chopping current feedback instrument amplifying circuit according to claim 2, wherein in the current feedback amplifying circuit (1), the feedback transconductance Gm2 and the input transconductance Gm1 have the same structure, the gates of the PMOS transistor M5 and the PMOS transistor M7 and the gates of the PMOS transistor M6 and the PMOS transistor M8 are respectively connected to external bias voltages VB1 and VB2, so that the current flowing through the feedback transconductance Gm2 is equal to the current flowing through the input transconductance Gm1, the drains of the PMOS transistor M1 and the PMOS transistor M3 and the drains of the PMOS transistor M2 and the PMOS transistor M4 are connected in pairs and are connected to the input end of the cascode amplifier A1 through two ends of the chopper in common, after the input transconductance Gm1 and the feedback transconductance Gm2 convert the corresponding input voltage and the feedback voltage into the input current and the feedback current respectively, the high-gain cascode amplifier A1 is responsible for the difference of the currents at the common source and the common source to ensure the accurate matching, since two ends of the input electrode of the feedback transconductance Gm2 are respectively connected to two ends of the resistor Ri, the current of the two ends of the feedback transconductance Gm2 is equal to that of the input transconductance Gm 1; the two-terminal current, therefore, the closed-loop gain of the current feedback amplifying circuit has:in the formula VinFor inputting differential signals, RiIs the resistance value of the resistor Ri, RonIs the resistance value of the resistor Ron, RopIs the resistance of the resistor Rop.
8. A chopped current feedback instrument amplifier circuit with low noise according to claim 6, characterized in that said residual ripple filtering circuit (2) usesThe structure is a second-order Sallen-Key filtering structure, wherein the grids of a PMOS tube M27 and a PMOS tube M28 in a transconductance amplifier are respectively connected with the common drain end of a PMOS tube M36 and an NMOS tube M38 and two output ends Von and Vop formed by the common drain end of the PMOS tube M37 and the NMOS tube M39 to form a full differential single gain buffer, a resistor Rn1, a resistor Rp1, a resistor Rn2, a resistor Rp2, a capacitor Cn1, a capacitor Cp1, a capacitor Cn2 and a capacitor Cp2 form a filter capacitor and a filter resistor of the whole second-order filtering circuit, and the transfer function of the obtained second-order filtering circuit is as follows:wherein,fc is the cut-off frequency of the filter circuit, Q is the quality factor of the filter circuit, Rn1Is the resistance value, R, of the resistor Rn1n2Is the resistance value, C, of the resistor Rn2n1Is the capacitance value, C, of the capacitance Cn1n2The cut-off frequency of the filter is adjusted by adjusting the resistance value and the capacitance value of the capacitor Cn2, so as to better filter out the ripple.
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