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[SOLVED] 30mV systematic offset - folded cascode

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gujaratibhai

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Hello,

This is my second ever post here. I have been a lurker for quite some time and love coming here now and then.

Well I am struggling with a 2-stage amplifier design.

I am designing a 2-stage, nmos input pair folded cascode amplifier. I am happy with DC gain, GBW, quiescent current, etc except for the Systematic offset. And I do not know where it's coming from. I have Johns Martin book and read through the section on systematic offsets but no avail.

The second stage gain device is a 3V nmos and i even replaced with 1V nmos device. The systematic offset (30mV) didn't go away.

Can you help? Maybe there is obvious fact I am missing or maybe there is something subtle going on. Thanks a lot,

Regards
Gujarati bhai

 

Guys

My diff pair was asymmetric. Dumb dumb dumb.

Thanks,
 

I see SOLVED mark so I assume that You found difference dimensions of your input pair mosfets? You have also unbalanced output stage and first stage which can produce additional offset.
 

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