can't get 2 precission multiply MDAC for pipeline ADC.

[kazu_kazu]

Dear all member,

I design 1.5 bit MDAC,:
using gain boosting folded cascode opamp
DC gain : 80 dB
UGB : 100MHz

but after I set it up with sc circuit, (2 precission multiply )
I can't get the rsult, sometimes output is bigger 1. ... Vin

but sometimes output even smaller than input.

do anybody knows what is the problem?
thank you very much


kazu



)

 

[BackerShu]

Some specific descriptions about your schematic or netlists may help to do locate your problem.