hi,
  while reading comparators i got the this doubt, normally for Reducing offset voltage we used to keep preamp infront of the latch and then offset cancellation to latch.Why can't we apply cancellation directly to latch? what i feel for cancellation we need to put amp in feedback while charging offset on cap, where as comparator may not be work in loop, is this correct?

Thanks,
rajasekhar.

hi,
   it's better than preamp, because comparator has -ve impedance.

thanks,
Rajasekhar.

hi,
 thanks for your reply, actually i am talking in the contest of the flash converters, there people are doing all these interpolation to reduce no of preamp. If we some how do offset cancellation to latch why they are puting so many preamps?

i feel following are the reasons

1. For a latch we need to use input offset storage (due to comparators high gain it may saturate if we use output storage), so while input storage we have to put latch in feedback so i am expecting stability problems and probabaly we may endup doing frequency compensation it may slow down our comparator.

2.Generally latch offset is more than preamp, so we need to wait more time to charge that offset on a cap

Sorry for the big mail..please correct me if any thing wrong

Thanks,
Rajasekhar.