phase margin and gain margin op amp

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biolycans

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Hi,

I designed an operational amplifier two stages cmos and what I want to do is to verify the phase margin and gain margin of this circuit. What configurations should I use for this circuit ?

Regards

Joaquin
 

PM and GM are important in a closed loop ckt like a buffer. In open loop configuration the 2stage op-amp is more like a comparator.
So you can use any closed loop configuration, simplest being an unity gain buffer. Then just do a stability analysis and find the PM & GM and compensate accordingly.
 

SIDDHARTHA HAZRA said:
So you can use any closed loop configuration, simplest being an unity gain buffer. Then just do a stability analysis and find the PM & GM and compensate accordingly.
Click to expand...

Just to avoid misunderstandings:
Unty gain applications with 100% feedback are the most critical configuration as far as the stabilty is concerned.
However, determination of stability margins is done using open-loop configuration (loop gain).
For unity-gain feedback this is identical to measure/simulate the opamps open-loop gain (magnitude and phase).
 

LvW said:
For unity-gain feedback this is identical to measure/simulate the opamps open-loop gain (magnitude and phase).
Click to expand...

Yes you are correct .... I forgot to mention that ... Thanks
 

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