I am working on a device to read very small voltage differences across the skin when 5 µA of current at frequencies from 10kHz to 2.5 MHz is passed through it. I do not know the exact range of voltages, but I expect it to be on the order of µV to mV. Does anyone know of an instrumentation amp that could differentiate these voltages and meet the other requirements? I have read Analog Device's in-amp guide, but I am still not sure of which would work best for this application. Any suggestions would be greatly appreciated.