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preamp used in comparators

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rmadhukarthi

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reduce kickback comparator

in comparators(latched comparators) very low gain pre-amplifiers are used . what is the use of this pre-amp.
 

the pre-amplifier amplify the input signal to increase the speed of comparator, because larger the difference to latch, faster the speed the latch make a decision
 

also reduce the kick back noise
 

what is the kick back noise?
any help is appreciated very much.
 

jhan_wzx said:
what is the kick back noise?
any help is appreciated very much.
Click to expand...

kickback noise is that the large excursion of comparator output couples to the circuit preceding comparator through parasitic capacitance
 

The pre-amp is used to reduce the kickback noise, and to decrease the input referred offset voltage of the latched comparator - note that there are a number of techniques to reduce the offset voltage of the pre-amps (averaging, offset sampling), but almost no technique to reduce the offset of the latched comparators.

Regarding the kickback noise you may want to check the paper referred on:



which in addition to discussing offset reduction techniques also has a good tutorial on existing CMOS latched comparators.

Regards
 

the preamplifer amplifies the difference between the two signal so that the comparator can compare clearly
 

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