q0w1e2r3
Junior Member level 1
Re: help,common mode voltage swing in fully diffrential opam
hi,everyone
when i'm dealing with the simulation of a fully differential opamp in spectre,a puzzle baffle me.The schemetic and result is as follows.
Common mode voltage selected by me equals 900mV,i use sc common mode feedback and telescope opamp for simplicity.i use this closed feedback(T&H) to achieve doubling the input voltage accurately.the clock is non-overlapping.
When i simulate in spectre i find the diffrence mode volatge doubled ,that's right.
but the common mode voltage swings from 730mV to 900mV.Why?is that becuse of dc offset or something else?how can i overcome it.in addition ,if i cascade series of such circiut as pipeline ADC,is this harmful?(assuming using fully differential opamp and common mode input range is wide enough)
Added after 2 minutes:
hi,everyone
when i'm dealing with the simulation of a fully differential opamp in spectre,a puzzle baffle me.The schemetic and result is as follows.
Common mode voltage selected by me equals 900mV,i use sc common mode feedback and telescope opamp for simplicity.i use this closed feedback(T&H) to achieve doubling the input voltage accurately.the clock is non-overlapping.
When i simulate in spectre i find the diffrence mode volatge doubled ,that's right.
but the common mode voltage swings from 730mV to 900mV.Why?is that becuse of dc offset or something else?how can i overcome it.in addition ,if i cascade series of such circiut as pipeline ADC,is this harmful?(assuming using fully differential opamp and common mode input range is wide enough)
Added after 2 minutes: