Re: [SI-LIST] : Parallel Plate Capacitance for Bypass

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From: Ray Anderson (raymonda@ha1mpk-mail.eng.sun.com)
Date: Fri Mar 24 2000 - 15:13:56 PST


The capacitance doubles because you have the capacitance
of the power plane to the top ground in parallel to the
capacitance of the power plane to the bottom ground.

Ctotal = Cpg1 + Cpg2

------------Ground 1-----------
                        |
                       === Cpg1
                        |
------------Power-------------
                        |
                       === Cpg2
                        |
-----------Ground 2-------------

Of course all this assumes that ground 1 and ground 2 are
solidly stiched together with lots of low Z vias.

-Ray

>
> This sounds very much like two caps in series to me so the value would
actually
> go down by 1/2 assuming the er and h are the same for both caps. Somehow,
> though,
> this doesn't *feel* right to me. I think I am missing something here.
>
> ----->Chris
>
>
>
> >
> >
> > 2. If you have a power plane sandwiched between 2 ground planes, does the
> > parallel plate capacitance double for a given area?
> >
> > Thank you,
> > Chris Hansen
> > Sr. Design Engineer
> > DPT & Adaptec Companies
> >
>
>

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