Subject: RE: [IBIS-Users] Wire characteristics
From: Ingraham, Andrew (Andrew.Ingraham@hp.com)
Date: Thu Oct 31 2002 - 12:49:57 PST
> Looking for curves of Lo and Co vs frequency for 22 guage wire.
Both Lo and Co are strongly (i.e., mostly) dependent on the
separation between the wire and the return path, usually ground.
If the wire is not placed close to a ground plane, you may have
a hard time quantifying them. (You need to ask: capacitance to
what?) Think about the characteristic impedance of just a wire
by itself. Is there one? Zo = sqrt(Lo/Co).
There are formulas for the inductance of a wire alone, but these
are relatively useless because the self inductance of a straight
wire is moderately meaningless. You really need to look at the
loop that the current takes, out and back.
If you want an earful on the subject, you could direct this question
to the Signal Integrity si-list on freelists.org.
Regards,
Andy
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