From: John Woodgate
Subject: Re: Ceramic Capacitors
Date: Wed, 2 Oct 2002 16:48:55 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Wed, 2 Oct 2002 17:58:14 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that ricardo wrote
(in <3D9B0373.AF27726E@erckert-ibe.de>) about 'Ceramic Capacitors', on
Wed, 2 Oct 2002:
>I suspect this rather is a resonance of the capacitor together with the
>parasitic inductance (board trace, capacitor itself). Be aware even an
>SMD component has a certain length and a magnetic field arround if an AC
>current flows! In case you have two capacitors in parallel you have a
>parasitic inductance between them. This may act as a parallel resonant
>tank with capacitive tap.
All that is true, *except* that the effect I am talking about is NOT due
to resonance with stray inductance. This si shown by the fact that
resonances can be detected at harmonically-related frequencies, which is
not so for tuned circuits.
It is a property of the material itself, **somewhat, but not very**,
like the resonance of a quartz crystal. 'Not very', because the bulk
material is not significantly piezo-electric.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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