Hi, I am designing a two stage differential amplifier with different i/p common mode voltage and o/p common mode voltage. When I connect it in closed loop using resistors R2 and R1 , dc current will flow due to difference in common mode. Is it ok for dc current to flow when the amplifier will be used in closed loop ? I want to characterise the closed loop response like step response etc.. Thanks
In the electronic world it is usual to describe circuits with schematics just to know what in the world you're talking about. Anyway, what about adding a buffer stage at the second stage output just to decouple output biaasing effects on the attenuation resistor divider?
In the first order, it's the resistive load by the feedback resistors that affects amplifier gain, not the dc output current. A two stage fully differential amplifier is surely far from an ideal amplifier, adding output buffers can be a step to improve it.