I have to make a AC to DC circuit. I have 10 uV to 1 mV (+ or -) on
> the input. the output have to be 50mV to 5 V,(one polarity only) to
> drive a VCO.
This is not really called an "AC to DC circuit" and you cannot achieve DC amplification of those minute signal levels with ordinary op amps, you must go to chopper amps or zero offset sampling of some kind.