Re: [SI-LIST] : PCB impedance variation v.s. layout pattern

Doug McKean (
Sat, 28 Aug 1999 14:11:15 -0700 (PDT)

Sorry, there's a classic case of thinking one
thing and saying another. I was thinking of
the "plate distance" adding. The "capacitance"
of caps in series is 1/Ctot = 1/C1 + 1/C2 + ...

What's interesting with the case originally asked
is that characteristic impedence is theoretically
immune to length. Thus, even if the meandering
does add more capacitance from it's relationship
with the ground plane, it also adds more inductance
because of the increased length. Since characteristic
impedence is dependent on the per length values of
capacitance and inductance, it would require IMHO,
the addition of another parameter in order to
change the CI.

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