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Can we do offset cancelling like this?

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benchen

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A comparator with pre-amplifer and latch usually does offset canceling like the first diagram. But I am asked to do offset cancelling according to the second diagram. Is it possible to do input offset cancelling inculding the latch. There are posive feedback in latch and I think there are problems if we connect it in a negative feedback loop.
 

I don't think you can do like the second diagram.
The input offset storage need the preamplifier closing a unity gain feedback. The feed back must negative. The latch is posive feedback only stable at high or low level voltage. If the loop include the latch how do you guarantee the loop stable or not latch to some level and the feedback is negative.
 

I think the second add some addtional offset .
 

interesing thinking
can you try it and tell me the result ~~!
tanks~!!
 

i think this will help

now i am designing also a comparator but i think the best idea is to make preamplifier from 4 cascoded low gaine amplifiers and use output and inoput offset storage
 

Comparing these two figures, I think you want to cancel the offset voltage of preamp and latch. but for conventional latch, when the latch works on 'nonlinear' .
. when the switch is 'on' and the latch is in 'reset', the latch output is all vdd(or a common mode voltage), so the input voltage opamp reset to vdd, the capacitors have not storage any offset information. so for conventional latch this structure can not cancel the preamp and latch offset.

if this structure can cancel the preamp and latch offset, the latch must design to work on linear region when the switches are 'on'.
 

i think it can be done but in the moment you want to estimate the latch offset you have to break the latch feed back so the latch works as an amplifiert
 

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