differencial biopotencial amplifier

[lean]

biopotencial

I am working with a differencial biopotencial amplifier based on two coupled buffers and a common instrumentation amplifier.

Why must be ac-coupled the bipotential amplifiers??

Thanks

 

[Regnum]

biopotencial

Biopotentials are usually mounted on some DC voltage, depending on the kind of electrodes and electrolyte that you're using.
You may use DC coupling with lower gain ampliflying at the 1st stage, so remove the DC voltage at the 2nd one.