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How to keep the impedance high while using AC coupling with In-amp

Question asked by Zifang on Jun 20, 2014
Latest reply on Jun 26, 2014 by Zifang

Hi dear all,

I have a problem with the AD8421 instrumentation amplifier. I need a input impedance at least 100MegΩ. But I want to use the AC coupling in front. That means I have to provide the return current pathway to the ground which limit the input impedance back to 1Meg from 10G. Is there anything I can do to increase the input impedance? From what I understand right now, as long as there's input bias current, I must to provide the pathway to route it to the ground.  This means I cannot really use the input impedance that the amplifier provide.

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