RE: [SI-LIST] : Stub Capacitance calculation

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From: Ron Miller (rmiller@Brocade.COM)
Date: Wed Jul 26 2000 - 11:41:53 PDT


There is a problem with this simplistic approach, and that is that the quarter wave effect
becomes more important than the capacitance as frequencies get into the Gigahertz
range. If you must use SPICE then capacitance probably is the best you can do, but
regardless of the capacitance, as the stub approaches 1/4 wavelength, it approaches a
short in the frequency domain. This is real, not just theory.

Ron Miller

> -----Original Message-----
> From: Mendelsohn, Joseph P (Joseph)
> Sent: Tuesday, July 25, 2000 12:02 PM
> To: 'Prasanna S'; 'si-list@silab.eng.sun.com'
> Subject: RE: [SI-LIST] : Stub Capacitance calculation
>
> Check the url below for an Online calculator. It reports Co/unit length
>
> http://www.emclab.umr.edu/pcbtlc/microstrip.html
>
>
> -----Original Message-----
> From: Prasanna S [mailto:prasan@hclt.com]
> Sent: Tuesday, July 25, 2000 1:23 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: [SI-LIST] : Stub Capacitance calculation
> Importance: High
>
>
> Hi All,
> How can I calculate the Capacitance of a Microstrip trace Stub
> with the trace routed in the component or top layer with a di-electric
> thickness of 3 mils under the trace.The di-electric constant is Er=4.0.
> and copper is 0.5 oz Can you give me the formula used for that? I am
> looking for the answer in pF/inch.
>
> Regards,
> Prasanna
>
>
>
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