help: why?? about comparator

[batistuta]

hi, everyone,
i have a question as follows:
In the offset cancellation mode, the OPAMP operate in open-loop mode, so the input offset amplify by its gain, therefore the low-gain amplifier should be used to ensure the operations in the active region under maximum input dc offset voltage.
why?? why not use high gain amplifier? the attchment is the schematic.
thanks...
Ffdong

 

[jerryzhao]

If the gain large, offset can let op's output saturation.

 

[8k-rom]

I think the first stage is a pre-amplifier, and its typical gain is about 10 ~ 40

refer to '' Baker CMOS Circuit design,layout and simulation ''

plz~

 

[DZC]

Maybe to prevent the slewing in the first stage is another concern.