Hi,
I have folded cascode amplifier but it not gives good PSR. With AC source on Vdd, look at differential output (in monte carlo) and PSR rises to -20dB at 10MHz, then drops. At low freq I understand - noise rejected by opamp gain. At high freq, PSR improves because AC supply noise shorts through output cap. But at medium freq, what sets PSR?
Please see attached diagram. VbFCPmos and Vbias set by ideal VDC source. VbFCTopPmos and Vcmc set by current mirror. So noise on PM3/4 source changes drain current? Or doesn't change drain current as VbFCTopPmos itself set by mirror (which also moves with supply)? How do PM3A/4A affect PSR? I need -50dB at 10Mhz, how I improve medium freq PSR?
Ansu