Electronic – Instrumentation Amplifier with Common Mode Feedback output

common-modefeedbackinstrumentation-amplifier

I'm currently attempting to design a small circuit that takes in a differential signal at < 4mv. I want to amplify this by around 1000 times.

I was reading up on Instrumentation Amplifiers, and they seem to do what I want to do, but I would also like to get the common mode signal as an output.

Are there any ICs out there that act as instrumentation amplifiers, but also have a pin outputting the common mode signal?

Best Answer

I haven't seen an InAmp chip with a dedicated common mode output.

I've used the circuit below to gleam the common mode voltage. Notice that gain-setting resistor RG is split into 2 equal parts R5 and R29.

I haven't thoroughly tested the accuracy of this common mode output. I only needed an approximate common mode voltage for a driven guard.

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