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Design >> Analog Design >> comparator diff pair
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Message started by newic on Aug 19^th, 2014, 7:23am

Title: comparator diff pair
Post by newic on Aug 19^th, 2014, 7:23am

hi

For a analog type comparator, shall the diff pair in saturation or linear? If it is in saturation, it causes its size bigger and slow down the speed, where speed is important.

tradeoff between gain vs speed?

Title: Re: comparator diff pair
Post by aaron_do on Aug 19^th, 2014, 7:32am

Perhaps you should clarify what you mean by "analog comparator". Is the output latched? Is the differential pair directly connected to the latch or is it part of the pre-amp?

Aaron

Title: Re: comparator diff pair
Post by loose-electron on Aug 19^th, 2014, 6:04pm

generally you want the device to function as an amplifier with common mode rejection. Therefor in saturation.

Title: Re: comparator diff pair
Post by carlgrace on Aug 19^th, 2014, 10:38pm

OP didn't say if the comparator was dynamic of if the diff pair was a pre-amp in front of the latch. Changes the answer.

Unless you know what you're doing though, a linear amplifier in front of the latch is usually a good idea.

Title: Re: comparator diff pair
Post by newic on Aug 24^th, 2014, 12:45am

got it thx. but it slow down the speed.

Title: Re: comparator diff pair
Post by analog_rf on Sep 26^th, 2014, 3:39am

putting input transistors in linear will lessen your resolution(difference between inputs for which output is high).