The 'resonant frequency' is a result of the capacitor's
value and the 'parasitic' or 'series' lead (wire) inductance.

Nature respects these factors and renders up a corresponding
'series resonant frequence'.

Using these 'naturally occuring' factors at RF frequencies has
been a mainstay of design in years past (when 'leaded' ceramic
disc caps or dipped mica caps were predominant) - this is not
so desireable a factor when the intent is to bypass a wide range
of 'frequencies' to ground as in logic 'bypass' caps.

Jim P

----- Original Message -----
From: William Chops Westfield <billw@CISCO.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, June 09, 2000 1:39 AM
Subject: Re: [EE]: 5V Logic Bypass caps - SMD value/phy sizerecomm


>    We are still left with the fact that the resonant frequency of a
>    capacitor is a fixed parameter for the part and cannot be move.

What has resonant frequency got to do with it, anyway?  I thought
resonance would come into play when you're trying to amplify a signal
at a particular frequency, not when you're trying to supress it?
Sure, you want the time contant of the RLC system to be small compared
to the times of your switching transients (otherwise, it'd be
equivilent to your bypass cap not having a chance to recharge before
the next current spike is required), but I don't see the advantage of
being actually NEAR a resonant frequency.  Aren't you really hoping
for a a series of overdamped step responses?

BillW