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So far it seems that the Unity amplifier set up is the best at suppressing EMI noise in a common mode-rejection setup. Interestingly, by reducing the resistor values the amplifier was better at suppressing the EMI noise. But adding decoupling capacitors add little to no affect (if not worsen) to the EMI suppression. My current speculation is that the lower variation on resistance allowed for the better better resistor matching, thus improving the rejection of EMI. Next time I would like to try lower tolerance resistors and another common-mode rejection setup that uses a ferrite choke coil instead.
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