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pre amplifier in the comparator

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shanmei

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HI,

for design the comparator, usually add a pre-amplifer to amplife the input signal to speed up the comparator. the comparator in the figure is a wide-spread one, but how to add a pre-amplifer to the compatator, here i will use it in the pipeline adc , the comparator will judge the +/- (Vref/4). Can I add a pre-amplifier directly to the inputs of the comparator, or some other circuit is useful. any useful paper?
Thank you.[/youtube][/url]
 

Hi guy
plz refer to Allen's book "CMOS analog integrated circuit design" chapter 8 ,there is detail explanation about this comparator.

B.R.
 

Hi
if u add a preamp before ur comparator, the threshold voltage no longer determined by the backend comparator, but determined by the pre-amp.
so u must set the threshold of ur pre-amp at VREF/4. :D this is my opinion !

B.R.
 

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    shanmei

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Preamp alse decrease the random offset of comparator,I think
 

One possible suggestion on this is to split reference subtraction and positive-feedback slicer.

If you use a cell to do reference subtraction, and then restore full-logic level of the subtracted signal. Between them, you can do pre-amplification of the residue.
 

chenjia said:
Preamp alse decrease the random offset of comparator,I think
Click to expand...

You are right, so you must also use offset cancelattion technics
 

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