Alt-BEAM Archive

Message #11160



To: beam@sgiblab.sgi.com
From: John Bachman bachman@anatek.mv.com
Date: Sat, 26 Feb 2000 20:12:52 -0500
Subject: Re: numeric symbol for a .1pf ceramic cap



> I am trying to read between the lines here, so if I am way off base please
excuse me. It sounds like you are trying to build a very high frequency
clock oscillator and therefore need a very small timing capacitor.
>
> If so, you have a couple of problems. First, the value of 0.1pf is
extremely low and probably not available. As I mentioned before, two
parallel pc runs or wires can easily have 0.1pf of capacitance between them.
Hence any circuit components would be insignificant. Also, the series
inductance of wires/pc runs would become a significant factor. You need
another approach.
>
> Secondly, a ceramic capacitor is a poor choice for a timing capacitor
because of it's wide value tolerance and thermal characteristics. Ceramics
are generally used only in decoupling and other applications in which the
value is not critical to the circuit function.
>
> With more details I can probably help more.
>
> John
>
> At 06:23 PM 2/25/00 , you wrote:
> >it's for a processor clock
> >
> > |___|
> > -------O()O-------
> >James Taylor
> >URL: http://fly.to/springmeadows
> >----- Original Message -----
> >From: John Bachman
> >To:
> >Sent: Monday, February 28, 2000 4:23 PM
> >Subject: Re: numeric symbol for a .1pf ceramic cap
> >
> >
> > > 0.1pf? That is an extremely low value. The capacitance between two
> >parallel pc runs is in that area. May I ask why you want it?
> > >
> > > John
> > >
> > > At 04:12 PM 2/25/00 , you wrote:
> > > >Does anyone know the numeric symbol for a .1pf ceramic cap. Or
knows a
> > > >site where I can look such data up?
> > >
> > >
>
>

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