how to immprove phase margin- ota

[satyanitt]

SIR,
im designing an OTA telescopic wid certain gain enchancement modification architecture wid current mirror technique crosscoupled....in .018 technology...
i got my gain enchanced by 6 db bt my phase margin got very much decreased to 54 from 78.... what shud i do to bring pm to more than 60 ...i took currents as 200uA for the ota...suggest me few thngs...plz

 

[leo_o2]

Pls post the detail structure and load conditions.

 

[satyanitt]

my spec is load capacitance is 2pf

 

[sutapanaki]

why not increase the load capacitors? You can also reduce the ratio of the mirror branch to the ota branch to reduce the capacitance at the NMOS cascode node - this is your non-dominant pole. You may also want to increase the gm of the NMOS cascode devices.

 

[leo_o2]

Yes. I also suggest increasing output capacitor.
And please try to add series-connected resistor on output capacitor.