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Req Help - fully differential op-amp

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arpit_655

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Hi all,

i`ve designed a gain boosted folded cascode fully diff op-amp with 100db gain & 700MHz UGB.

i tried with putting differential-to-single-ended stage but it was causing the op-amp to be highly Unstable...

could someone tell me how to configure a fully differential op-amp as voltage follower (unity gain feedback).

Waiting for a quick reply..
Regards.
 

eda4you

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Make simulation and make a bode plot. (Look also for a rebound of the phase). You should have at least 60° phase margin.
 

arpit_655

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i have 70 deg of phase margin while taking differential output....

but when i put next stage to get single ended output then phase reached -220 deg
making the op-amp highly unstable....

is it possible to use a fully differential op-amp as a buffer in chage scaling D/A converter... plz suggest a way...
 

Btrend

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arpit_655 said:
i have 70 deg of phase margin while taking differential output....

but when i put next stage to get single ended output then phase reached -220 deg
making the op-amp highly unstable....

is it possible to use a fully differential op-amp as a buffer in chage scaling D/A converter... plz suggest a way...

do u include ur next stage as load while in runing AC simulation of ur differential amp ?
 

arpit_655

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next stage is a differential amplifier with active current mirror...
 

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