Instrumentation amplifier and band-pass filter

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meereck

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Hello,
I am using an AD620 circuit to amplify a differential signal having about 100kHz.
Since the signal contains noise, I would like to employ a band-pass filter to the both amplifier inputs?

Do I need separated amplifier to build a filter or it can be achieved with AD620 chip only (and adding just some resistors and capacitors)?
Would anybody please have any circuit/scheme?

Thanks in advance,
regards Meereck
 

I think you don't have enough access to the intermediate
nodes, to do a good job on the filtering using the AD620
itself. You could low-pass both of them to ground,
beforehand, though. Maybe scrounge a common-
mode choke out of some dead power supply's line input
path, but that might roll off too much of the desired signal
as well (?).

Can you see with a 'scope, whether the amplifier is being
bothered by the noise (like you get more noise out, than
the difference-noise would make you expect)? If it's not
producing nonlinear behaviors then maybe an output
bandpass would be easier / cleaner.
 

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