analog_ambi
Member level 1
i have designed a low power beta multiplier refernce (70nA) as shown. The opamp is a 5T diff pair.To check for stabilit i broke the -ve feedback loop and plugged iprobe from analoglib in cadence. stb analysis shows phase margin of 20 deg and gain margin of 14dB with C=2pf. I m not able to achive better phase margin even after shifting the mirror pole of the 5T diff pair. A phase margin of 60 requires C of 100p. The transient response with step Vdd (1us rise time) is shown as attached which is not quite stable. Can i expect it to work if tapped out?
Lastly, even if i achieve PM of 60 deg with C=100pF, the transient response is till the same which is shocking to me!! Pls help
Lastly, even if i achieve PM of 60 deg with C=100pF, the transient response is till the same which is shocking to me!! Pls help