阅读说明：本技术 一种低功耗斩波放大器电路 (Low-power consumption chopper amplifier circuit ) 是由 张瑛 蒋文超 张靖宇 周梦波 于 2020-12-25 设计创作，主要内容包括：一种低功耗斩波放大器电路,包括复用的第一放大器和第二放大器,其中,两个放大器的第一级进行复用；第一放大器和第二放大器的第二级对复用的第一级的输出进行重组,构成各自的输出。本电路将两个放大器复用第一级,可节省其中一个放大器第一级的电流,有效地减小了模拟前端电路的功耗,将噪声更低的放大器作为提供心电信号放大倍数的放大器以减小模拟前端电路整体的等效噪声。(A low-power consumption chopper amplifier circuit comprises a first amplifier and a second amplifier which are multiplexed, wherein the first stage of the two amplifiers is multiplexed; the second stage of the first and second amplifiers recombines the multiplexed first stage outputs to form respective outputs. The circuit multiplexes the two amplifiers into the first stage, so that the current of the first stage of one amplifier can be saved, the power consumption of the analog front-end circuit is effectively reduced, and the amplifier with lower noise is used as the amplifier for providing the electrocardiosignal amplification factor so as to reduce the integral equivalent noise of the analog front-end circuit.)

1. A low-power consumption chopper amplifier circuit, characterized by:

the amplifier circuit comprises a first amplifier and a second amplifier which are multiplexed, wherein the first stage of the two amplifiers is multiplexed; the second stage of the first and second amplifiers recombines the multiplexed first stage outputs to form respective outputs.

2. A low-power consumption chopper amplifier circuit as claimed in claim 1, wherein: the first stage of multiplexing comprises transistor M1, parallel transistors M2 and M3 connected thereto, parallel transistors M4, M8 and M5, M9 connected to transistor M2, parallel transistors M6, M10 and M7, M11 connected to transistor M3, and transistor M12 connected to ground.

3. A low-power consumption chopper amplifier circuit as claimed in claim 2, wherein: transistors M2 and M3 receive Vin1+, Vin1-, respectively, as the two inputs of the first amplifier.

4. A low-power consumption chopper amplifier circuit as defined in claim 2, wherein: transistors M4, M7 and M5, M6 receive Vin2+, Vin2-, respectively, as the two inputs of the second amplifier.

5. A low-power consumption chopper amplifier circuit as claimed in claim 1, wherein: in the second stage, the second stage of the first amplifier includes transistors M13 and M14 connected in parallel, transistors M15 and M16 connected in parallel to transistor M13, and transistors M17 and M18 connected in parallel to transistor M14, as well as transistor M19 connected to ground; the second stage of the second amplifier includes transistors M20 and M21 in parallel, transistors M22 and M23 in parallel connected to transistor M20, and transistors M24 and M25 in parallel connected to transistor M21, as well as transistor M26 connected to ground.

6. The chopper amplifier circuit with low power consumption according to claim 5, wherein: transistors M15, M16, M17, M18 and transistors M20, M21, M22, M23 receive the first stage output of the multiplexed amplifier, respectively.

Technical Field

The invention belongs to the technical field of integrated circuits, and particularly relates to a low-power consumption chopper amplifier circuit.

Background

The electrocardiosignals record the state of heart activity, and the health condition of the heart can be evaluated and cardiovascular diseases can be diagnosed in an auxiliary way by analyzing the collected electrocardiosignals. The electrocardiosignal acquisition simulation front end is widely applied to wearable health monitoring systems. Due to the need of long-time real-time monitoring of the health monitoring system, the demand for low power consumption of the electrocardiosignal acquisition analog front end is increasing day by day.

Driven by the demand of the electronic industry, the research on portable electrocardiosignal acquisition is very wide. The electrocardiosignal is a periodic weak bioelectricity signal, the amplitude of the electrocardiosignal is between 0.1 and 5mV, the frequency of the electrocardiosignal is between 0.5 and 150Hz, and the electrode used for collecting the electrocardiosignal has direct current offset voltage. Therefore, the acquisition of the electrocardiosignals is easily interfered by the outside, and the low power consumption can realize the requirement of long-time work of the monitoring equipment. The anti-interference and low power consumption are the development directions of main electrocardiosignal acquisition circuits.

The analog front-end circuitry typically used for monitoring cardiac electrical signals needs to fulfill three basic requirements: 1. amplifying weak electrocardiosignals by 100 times; 2. as low noise as possible; 3. a high-pass pole is introduced into the circuit to suppress electrode offset voltage and low-frequency interference caused by physiological activities such as respiration. Under the condition of meeting the two requirements, the lower the power consumption of the analog front-end circuit is, the better the requirement of continuous long-time monitoring is. At present, a common analog front-end circuit for electrocardiosignal monitoring adopts a capacitive coupling amplifier to realize 100-time amplification, simultaneously adopts a chopping technology to reduce circuit noise, and needs an additional amplifier to construct a direct current offset cancellation loop to generate a high-pass pole to inhibit electrode offset. In the conventional structure, a chopping technique is usually introduced to reduce circuit noise, and after the chopping technique is introduced, at least two complete amplifiers are usually required to amplify a cardiac signal and suppress low-frequency interference, which increases the burden of circuit power consumption.

Disclosure of Invention

The invention provides a low-power consumption chopper amplifier circuit aiming at the problem that the traditional electrocardiosignal acquisition analog front end based on the chopper technology needs to use a plurality of amplifiers to consume large power, and the current multiplexing technology is utilized to recombine the first-stage output of the amplifiers so as to reduce the power consumption of the amplifiers.

A low-power consumption chopper amplifier circuit comprises a first amplifier and a second amplifier which are multiplexed, wherein the first stage of the two amplifiers is multiplexed; the output of the multiplexed first stage serves as the input to the first and second amplifiers.

Further, the first stage of multiplexing includes transistor M1, parallel transistors M2 and M3 connected thereto, parallel transistors M4, M8 and M5, M9 connected to transistor M2, parallel transistors M6, M10 and M7, M11 connected to transistor M3, and transistor M12 connected to ground.

Further, transistors M2 and M3 receive Vin1+, Vin1-, respectively, as the two inputs of the first amplifier.

Further, transistors M4, M7 and M5, M6 receive Vin2+, Vin2-, respectively, as two inputs to the second amplifier.

Further, in the second stage of the amplifier, the second stage of the first amplifier includes transistors M13 and M14 connected in parallel, transistors M15 and M16 connected in parallel to the transistor M13, and transistors M17 and M18 connected in parallel to the transistor M14, and a transistor M19 connected to ground; the second stage of the second amplifier includes transistors M20 and M21 in parallel, transistors M22 and M23 in parallel connected to transistor M20, and transistors M24 and M25 in parallel connected to transistor M21, as well as transistor M26 connected to ground.

Further, transistors M15, M16, M17, M18 and transistors M20, M21, M22, M23 receive the first stage output of the multiplexing amplifier, respectively.

The invention achieves the following beneficial effects:

(1) and the power consumption is reduced. The traditional electrocardiosignal acquisition analog front end adopting the chopping technology at least needs two complete amplifiers to realize the functions of introducing a high-pass pole and amplifying signals.

(2) The noise is reduced. According to the invention, the amplifier 2 is used for PMOS and NMOS complementary input according to different requirements of the electrocardiosignal acquisition analog front end on the amplifier, compared with the amplifier 1, the transconductance of the amplifier 2 is larger, and the corresponding noise is lower, therefore, the amplifier 2 with lower noise is used as an amplifier for providing electrocardiosignal amplification factors to reduce the integral equivalent noise of the analog front end circuit.

Drawings

Fig. 1 is a circuit diagram of a first stage of a multiplexing amplifier according to an embodiment of the present invention.

Fig. 2 is a circuit diagram of a second stage of the multiplexing amplifier according to an embodiment of the invention.

Fig. 3 is a circuit diagram of an application of a multiplexing amplifier in an analog front end of electrocardiosignal acquisition according to an embodiment of the invention.

Detailed Description

The technical scheme of the invention is further explained in detail by combining the drawings in the specification.

This embodiment multiplexes the first stages of two amplifiers, the second stages each recombining to form a respective output. FIG. 1 shows the first stage of two amplifier multiplexing, Vin1+, Vin 1-are the two inputs of amplifier 1, Vin2+, Vin 2-are the two inputs of amplifier 2, and Vo1, Vo2, Vo3, Vo4 are the first stage outputs of the multiplexing amplifier.

Let the transconductances of the transistors M2 and M3 be gm1, the transconductances of the transistors M4 to M7 be gm2, the transconductances of the transistors M8 to M11 be gm3, and the output resistance of the first stage of the multiplexing amplifier be Rout 1. Therefore, the output voltages of the four output branches of the first stage are respectively:

Vo1＝-1/2*Vin1*gm1*Rout1-Vin2(gm2+gm3)Rout1；

Vo2＝-1/2*Vin1*gm1*Rout1+Vin2(gm2+gm3)Rout1；

Vo3＝+1/2Vin1*gm1*Rout1+Vin2(gm2+gm3)Rout1；

Vo4＝+1/2Vin1*gm1*Rout1-Vin2(gm2+gm3)Rout1。

FIG. 2 shows the output stages of the two amplifiers, Vout1+, Vout 1-are the outputs of amplifier 1, Vout2+, Vout 2-are the outputs of amplifier 2. The respective output voltages are formed by recombination of the outputs of the first stage of the amplifier. Let gm4 be the transconductance of transistors M15-M18, M22-M25, and Rout2 be the output resistance of the second stage of the amplifier, so the output voltages of the branches of the second stage are:

Vout1+＝-(Vo1+Vo2)*gm4*Rout2＝+Vin1*gm1*Rout1*gm4*Rout2；

Vout1-＝-(Vo3+Vo4)*gm4*Rout2＝-Vin1*gm1*Rout1*gm4*Rout2；

Vout2+＝-(Vo1+Vo4)*gm4*Rout2＝+2*Vin2(gm2+gm3)Rout1*gm4*Rout2；

Vout2-＝-(Vo2+Vo3)*gm4*Rout2＝-2*Vin2(gm2+gm3)Rout1*gm4*Rout2。

vout1+ and Vout 1-are taken as the output of amplifier 1, Vout2+ and Vout 2-are taken as the output of amplifier 2. The output gain of the amplifier 1 is: av1 gm1 Rout1 gm4 Rout 2. The output gain of the amplifier 2 is: av2 is 2 (gm2+ gm3) Rout1 gm4 Rout 2.

VB1 and VB2 are bias voltages of the amplifiers and are used for setting the working states of the amplifiers; CMFB1, CMFB2, CMFB3 are common mode feedback voltages of the amplifier for stabilizing the output common mode point.

The amplifier 1 and the amplifier 2 are both two-stage amplifiers, so-called two-stage amplifiers, that is, the amplifier is formed by cascading a first-stage amplification and a second-stage amplification. The transistors M1 to M12 are the first stage common to the amplifier 1 and the amplifier 2, and can be understood as: m1 to M12 (first stage of amplifier) + M13 to M19 (second stage of amplifier 1) being amplifier 1; m1 to M12 (first stage of amplifier) + M20 to M26 (second stage of amplifier 2) become amplifier 2.

The circuit multiplexes the first stages of the two amplifiers, and the second stage of the amplifier is not multiplexed. The two traditional two-stage amplifiers need two first stages and two second stages, and the two first stages are made into one in the design so as to achieve the effect of low power consumption.

In the embodiment, the current consumption of the amplifier is effectively reduced by multiplexing the first stage of the two amplifiers, the amplifier 1 is used as an amplifier for eliminating an electrode offset voltage loop, and the amplifier 2 is used as an amplifier for amplifying electrocardiosignals. A specific circuit application is shown in fig. 3.

The amplifier 1, the integrating resistors Rint1 and Rint2, and the integrating capacitors Cint1 and Cint2 form an integrator, the low-frequency components of the outputs Vout1 and Vout2 are integrated, the voltage output by the integrator is modulated to a high frequency by a chopper1, and is converted into a current by the capacitors Chp1 and Chp2 to be fed back to the input end of the amplifier 2, so that the low-frequency components mixed in the electrocardiosignal are cancelled. Therefore, a direct current offset elimination loop of the analog front-end circuit is formed, a high-pass pole is introduced into the system, and the offset of a direct current electrode is restrained.

The amplifier 2, choppers 2 and 3, and a feedback system composed of input capacitors Cin1 and Cin2, feedback capacitors Cfb1 and Cfb2 realize 100 times amplification of the acquired electrocardiosignals, wherein Cin1 is 100 × Cin2 is 100 × Cfb1 is 100 × Cfb 2.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above embodiment, but equivalent modifications or changes made by those skilled in the art according to the present disclosure should be included in the scope of the present invention as set forth in the appended claims.