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.