[SI-LIST] Re: Decoupling capacitors

At 10:34 AM 5/21/2002 -0400, Wayne Cooke wrote:
>Hello all,
>
>I have had quite alot of grief with using small valued ceramic capacitors
>(in the 100pF-1000pF range) in parallel with large valued capacitors due to
>the parallel resonant tank circuits that are caused by the interaction of
>the capacitor parasitics.  This would cause our products to fail radiated
>emissions, and tweaking the capacitor values would only cause the resonant
>point to shift -- improving one harmonic but making another even worse.


Actually, when you shift resonant points, some really interesting (and 
helpful) things can happen. If you have not seen our article on bypass caps 
and the influence of ESR and self resonant frequencies on the impedance 
characteristics of the power system, you might find it helpful. You can 
find it on our web site at www.ultracad.com.

Doug Brooks


_______________________________________________________________________________
UltraCAD Design announces availability of its new book "Signal Integrity 
Issues in PCB Design"
Details at  www.ultracad.com


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