At 10:10 15/08/97 -0400, you wrote:
>Does anyone have a formula for calculating the distributed
>capacitance of copper planes? I Know I have seen this before
>in PCD magazine but I seem to have *lost* the issue.
>
>Thanks in advance for your assistance.
>
>Jeffrey McGlaughlin
>BFGoodrich Avionics Systems Inc.
>1105 Schrock Road
>Suite 800
>Columbus Ohio 43229
>(614)825-2232 (voice)
>(614)825-2037 (fax)
>[log in to unmask]
>

Jeff,

Not sure if this is what you're after:

Capacitance of a parallel plate capacitor (or parallel copper planes)
is given as:

      C = Eo x Er x A
          -----------
               D

Where:
       C  = capacitance in Farads      (F)
       Eo = permittivity of free space (8.854 x 10exp-12) (F/m)
       Er = relative permittivity  (typically FR-4 is 4.6 at 1 MHz) (no units)
       A  = area of the plates (or planes) (m x m)
       D  = distance between plates (or planes) (m)

This equation neglects fringing effects.

Best regards

Andy Burkhardt <[log in to unmask]>
Tel: + 44 1481 53081
Fax: + 44 1481 52476
http://www.polar.co.uk
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