Hi

        I have some very important differential pairs on a PWB that must
have a particular differential impedance.

        The problem is:  how can I specify this on the drawing sent to the
fab shop?

        Our usual method would be to call for a particular single-ended
impedance, which seems to be beating around the bush.     It work to a
point; but I think it leaves too many variables that could change the
differential impedance.

        Any thoughts on this?


Joe Hurst
PWB Designer
Computing Devices Canada
A General Dynamics Company
[log in to unmask]
613-596-7816

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