CN102082553B - Integrator of differential input - Google Patents

Abstract

The invention discloses an integrator with differential input, which comprises a differential signal source V _in , operational amplifiers A1, A2 and an instrument amplifier A3, and the two ends of the differential signal source V _in are respectively connected to the operational amplifier by connecting a resistor R in series through a wire. The inverting input terminals of A1 and A2, the output terminals of the operational amplifiers A1 and A2 are respectively connected to the inverting input terminal and positive input terminal of the instrumentation amplifier A3 through the series connection of the resistor R1 through the wire, and the output terminal of the instrumentation amplifier A3 is used as the total signal Output terminal: a capacitor C is connected in parallel between the positive input terminal and the output terminal of the operational amplifier A1 and between the positive input terminal and the output terminal of the operational amplifier A2. The invention can suppress the integral drift caused by the common mode voltage, so that the integral measurement is more accurate and the method is simple.

Description

Integrator with differential input

technical field

The invention relates to the field of integrators, in particular to an integrator with differential input.

Background technique

Integrators are mainly used in electromagnetic measurements of some devices. For example, in the process of tokamak discharge experiments, the output of many electromagnetic measurement diagnostic signals is the differential component of the signal. To restore the signal, an integrator is needed. However, the traditional analog integrators are in the form of single-ended input, as shown in Figure 1, which cannot overcome the integral drift caused by the common-mode voltage on the input. In order to better suppress the influence of the common-mode voltage on the integral effect, an integrator in the form of a differential input is required.

Contents of the invention

In order to solve the problems existing in the prior art, an integrator with differential input is provided, which adopts the form of differential input and can better keep the integration drift caused by the common mode voltage.

Technical scheme of the present invention is as follows:

An integrator with differential input, characterized in that it includes a differential signal source V _in , operational amplifiers A1, A2 and an instrumentation amplifier A3, and the two ends of the differential signal source V _in are respectively connected to the resistor R through a wire series connection The inverting input terminals of the operational amplifiers A1 and A2, the output terminals of the operational amplifiers A1 and A2 are respectively connected to the inverting input terminals and the positive input terminals of the instrumentation amplifier A3, and the output terminal of the instrumentation amplifier A3 is used as the output of the total signal terminal; between the positive input terminal and the output terminal of the operational amplifier A1 and between the positive input terminal and the output terminal of the operational amplifier A2 are respectively connected in parallel with a capacitor C.

The integrator with differential input is characterized in that: the potentials of the inverting input terminals of the operational amplifiers A1 and A2 are equal.

The integrator with differential input is characterized in that: the resistors R respectively constitute the integrating resistors of the operational amplifiers A1 and A2, and the capacitors C respectively constitute the integrating capacitors of the operational amplifiers A1 and A2.

Principle of the present invention is as follows:

Referring to the structure of a typical instrumentation amplifier, an integrator with differential input is designed. After the signal is integrated by two single-ended integrators at the front end, the integral result is subtracted by the differential amplifier at the rear end, and the integral result of the differential input is obtained, while the integral result of the common mode input is eliminated, thereby realizing the integration of the differential signal and suppressing purpose of common-mode signals.

Beneficial effects of the present invention:

The integrator with differential input provided by the invention can suppress the integral drift caused by the common mode voltage, so that the integral measurement is more accurate and the method is simple.

Description of drawings

FIG. 1 is a schematic diagram of the circuit structure of the present invention.

Detailed ways

Referring to Fig _. 1, an integrator with differential input includes a differential signal source V _in , operational amplifiers A1, A2 and an instrumentation amplifier A3. The inverting input terminals of A1 and A2, the output terminals of the operational amplifiers A1 and A2 are respectively connected to the inverting input terminal and the forward input terminal of the instrumentation amplifier A3, and the output terminal of the instrumentation amplifier A3 is used as the output terminal of the total signal; the output terminal of the operational amplifier A1 A capacitor C is connected in parallel between the positive input terminal and the output terminal and between the positive input terminal and the output terminal of the operational amplifier A2.

The potentials of the inverting input terminals of operational amplifiers A1 and A2 are equal.

Resistors R constitute integral resistances of operational amplifiers A1 and A2 respectively, and capacitors C constitute integral capacitances of operational amplifiers A1 and A2 respectively.

Due to the principle of "virtual ground", the potentials of the inverting input terminals of the operational amplifiers A1 and A2 are equal, so the input current corresponding to the inverting input terminals of the operational amplifiers A1 and A2 is I=V _in /2R. For the common-mode voltage V _CM generated by the differential signal source V _in , it is equivalent to adding a current of I _CM = V _CM to the inverting input terminals of the operational amplifiers A1 and A2, then the voltage values at the output terminals of the operational amplifiers A1 and A2 are respectively for: ${\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000048297920000011.png"\; state="\{\{state\}\}">V</figure-callout>}}_1=-\frac{1}{2\mathrm{RC}}{\&Integral;}_0^t{V}_{\mathrm{in}}\mathrm{dt}-\frac{1}{\mathrm{RC}}{\&Integral;}_0^t{V}_{\mathrm{CM}}\mathrm{dt},$ $V_2=\frac{1}{2\mathrm{RC}}{\&Integral;}_0^t{V}_{\mathrm{in}}\mathrm{dt}-\frac{1}{\mathrm{RC}}{\&Integral;}_0^t{V}_{\mathrm{CM}}\mathrm{dt},$ Assuming that the charge on the integrating capacitor C is 0 at the beginning, then the output voltage after passing through the differential amplifier is: $V_0=V_1-V_2=-\frac{1}{\mathrm{RC}}{\&Integral;}_0^t{V}_{\mathrm{in}}\mathrm{dt}.$

Claims (3)

1. an integrator for difference input, is characterized in that: include differential signal source V _in, operational amplifier A 1, A2 and instrument amplifier A3, described differential signal source V _inone end access the reverse input end of operational amplifier A 1, described differential signal source V after by wire series resistor R1 _inthe other end access the reverse input end of operational amplifier A 2 after by wire series resistor R2, and R1=R2, the output of described operational amplifier A 1, A2 directly accesses reverse input end and the positive input of instrument amplifier A3, and the output of described instrument amplifier A3 is as the output of resultant signal; Between the reverse input end of described operational amplifier A 1 and output and be connected to capacitor C 1, between the reverse input end of described operational amplifier A 2 and output and be connected to capacitor C 2, and C1=C2, and the positive input ground connection of A1 and A2.

2. the integrator of difference input according to claim 1, is characterized in that: the current potential of described operational amplifier A 1, A2 reverse input end equates.

3. the integrator of difference input according to claim 1, is characterized in that: described resistance R 1, R2 form respectively the integrating resistor of operational amplifier A 1, A2, and capacitor C 1, C2 form respectively the integrating capacitor of operational amplifier A 1, A2.

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