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Problem with a very low gain of OTA

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frankwen

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hi
when i simulated the ota in the picture
sometimes i found the gain was very low
it was about 30dB
even the gain at the output(the second stage) was samller than the first stage
Can anybody tell me why this happenned?
thank you.
 

about the ota's gain

Typical gain for such circuit is more 100dB (process > 0.5um). So at the first you need to check that each MOSTs operate in saturation. Also check CMFB circuit. I hope u don't forget include CMFB in simulation.
 

about the ota's gain

maybe your w/l is not in saturation
 

Re: about the ota's gain

frankwen said:
hi
when i simulated the ota in the picture
sometimes i found the gain was very low
it was about 30dB
even the gain at the output(the second stage) was samller than the first stage
Can anybody tell me why this happenned?
thank you.

DC operation may be error.
 

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