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how to immprove phase margin- ota

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satyanitt

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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

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Pls post the detail structure and load conditions.
 

satyanitt

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my spec is load capacitance is 2pfScreenshot.png
 

sutapanaki

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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

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

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