Differential Input and Differentiating Circuit

傅里叶的猫

Differential Input and Differentiating Circuit [Copy link]

I was reading a book on analog electronics recently, and suddenly I had an idea. Can the differential input of the instrumentation operational amplifier AD620 achieve the same difference-finding effect as the difference-finding circuit, that is, the output Vo = V1-V2? If so, then the AD620 can be used as a difference-finding circuit, and the gain can be adjusted, the noise is low, and the drift is low. Isn't it wonderful? (Multisim simulation of the two circuits has the same effect)

maychang

“Can the differential input of the instrumentation operational amplifier AD620 achieve the same difference-finding effect as the difference-finding circuit, that is, output Vo = V1-V2?”

Can.

But the difference between two single-ended signals can be achieved with other circuits. Whether it is suitable from the perspective of cost needs to be calculated.

傅里叶的猫

maychang published on 2019-6-23 09:07 "Can the differential input of the instrumentation operational amplifier AD620 achieve the same difference-finding effect as the difference-finding circuit, that is, the output Vo=V1-V2?" ...

Dear Sir, last time I asked you how to separate the DC bias in the signal, and last night I suddenly had an idea. If we use a diode circuit similar to a power rectifier bridge to shape the signal, can we achieve the effect of separating the DC bias?

maychang

Fourier's Cat posted on 2019-6-23 09:41 Dear, last time I asked you how to separate the DC bias in the signal. I suddenly had an idea last night. If we use a diode similar to a power rectifier bridge...

"If we use a diode circuit similar to a power rectifier bridge to shape the signal, can we achieve the effect of separating the DC bias?"

It can achieve the effect of separating direct current.

However, it is simpler and more accurate to low-pass filter the AC/DC mixed signal to obtain the DC component.

傅里叶的猫

maychang posted on 2019-6-23 10:24 "If a diode circuit similar to a power rectifier bridge is used to shape the signal, can the effect of separating the DC bias be achieved?" Yes...

Yes, from the simulation, the basic rectifier bridge can only flatten part of the waveform, which is quite different from the ideal DC signal.

maychang

Fourier's Cat posted on 2019-6-23 10:34 Yes, from the simulation, the basic rectifier bridge can only flatten part of the waveform, which is quite different from the ideal DC signal

The diode used for rectification is a strong nonlinear element. Strong nonlinearity means that it will inevitably bring errors and is difficult to correct. Even if the so-called precision rectification is used, the DC component in the mixed signal must be obtained after filtering, which is not as good as direct passive low-pass filtering.