Fully differential comparator

[Junus2012]

Dear friends,

I have fully differential outputs coming from from fully differential amplifier, I want to compare between them for the purpose of digital offset trimmming,

I have seen some people use two comparator like a window comparator, some use fully differential comparator

my question is that why not using normal comparator and I connect each output from the amplifier to one input of comparator,
why usually people use this type of comparator to compare when variable voltage to a constant voltage connected to the other input. Is there any problem to have differential inputs?

thank you

 

[dick_freebird]

There is no problem. There are influences of
input slew rate and overdrive on input offset
voltage and so on. And non-rail-rail-input
comparators can see the front end cut off
if both inputs head that way (often use
simpler front ends if one input's pinned
voltage can counted on).

 

[Junus2012]

Dear freebird

I have noticed also that might be another reason of people adopting fully differential comparator, that is because when they use it as a preamplifier to a latch compator, where the latch comparator must have differential inputs which is now coming from the fully differential preamplifier stage

Isn't right

thank you