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Design >> Analog Design >> comparator bandwidth
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Message started by lhlbluesky_lhl on Mar 22^nd, 2013, 4:43am

Title: comparator bandwidth
Post by lhlbluesky_lhl on Mar 22^nd, 2013, 4:43am

in normal case, comparator is used in open-loop, not in closed-loop as feedback-amplifier, so, how to decide the -3db bandwidth of open-loop comparator? is there some formula or guide for the -3db bandwidth calculation of open-loop comparator?
thanks.

Title: Re: comparator bandwidth
Post by wave on Mar 22^nd, 2013, 10:31am

Why not look at Propagation Delay instead?

Title: Re: comparator bandwidth
Post by loose-electron on Mar 22^nd, 2013, 4:39pm

You are trying to determine the BW of a non linear device.

That doesn't really make sense.

BW for a linerar device, yes, but comparators are typically characterized as a function of propagation delay or response time characteristics.

Title: Re: comparator bandwidth
Post by raja.cedt on Mar 23^rd, 2013, 2:28am

Hello,
in addition to jerry comments, there is lot to estimate for sampler and on the top of that bandwidth doesn't make scene much.

Have a look at this paps
1. Time Resolution of NMOS Sampling Switches Used on Low-Swing Signals

2.Characterizing Sampling Aperture of Clocked Comparators

Have fun,
Raj,

Title: Re: comparator bandwidth vs Propagation Delay
Post by weber8722 on Apr 11^th, 2013, 4:56am

Hi,

best check the delay for different input overdrive, e.g. have one input at 1V and the other with puls from a=0.9V to b=1.05V. Then vary both a and b in a loop. You will see that the delay becomes shorter for large b and large a!!
So there is no single number which describes such highly nonlinear circuit as a comparator.
Also there are different parts in response time: like pure delay (to get out of saturation, then a part for rise or fall time. :) :)

Bye Stephan