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Design >> Analog Design >> bypass cap calcualtion
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Message started by Mostafa Elwakeel on Mar 19^th, 2009, 5:05pm

Title: bypass cap calcualtion
Post by Mostafa Elwakeel on Mar 19^th, 2009, 5:05pm

Hello all ,

any one know how i can calculate bypass capacitors in low frequancy analog cirucit ??

thank you

Title: Re: bypass cap calcualtion
Post by wave on Mar 19^th, 2009, 6:06pm

I=C(dV/dT)

Title: Re: bypass cap calcualtion
Post by Ken Kundert on Mar 19^th, 2009, 7:07pm

See http://www.designers-guide.org/Design/bypassing.pdf

-Ken

Title: Re: bypass cap calcualtion
Post by loose-electron on Mar 22^nd, 2009, 5:01pm

Ken:

A pretty good writeup! I am presently dealing with a medical electronics problem and the original designer was totally clueless on anything above 10Khz - Its spaghetti inductors all over the place.

hope all is well
Jerry

Title: Re: bypass cap calcualtion
Post by Ken Kundert on Mar 23^rd, 2009, 9:22pm

Thanks Jerry.

Back in 1978 a very seasoned engineer at Tektronix by the name of Gene Cowan took me aside and explained the whole supply bypassing and decoupling story. Very simple if you understand what is going on, but rarely talked about in schools. Anyway, I though I would carry on his legacy by writing it up and putting in on the web. While I at HP I used one of their LCR meters to characterize the various components used for bypassing and decoupling, and ran into some weird, seemingly non-physical results, which eventually resulted in the papers on dielectric absorption, lossy inductors, and fracpoles. All in all, a rather interesting thread.

-Ken