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Derive CM voltage from AD8237 for RLD scheme.

Question asked by inauser on Mar 21, 2018
Latest reply on Mar 23, 2018 by krisf

I am thinking about using an AD8237 in a biopotential amplifier. I would like use a common mode feedback scheme to improve CMRR. I have prevously obtained the CM voltage from the mid point of two series connected resistors across Rgain. This is simple with a "3 amplifier" type INA as shown below. Where would I get a CM signal from in this new Gm topology- other than by adding resistors across the input?