FreeLists / si-list / [SI-LIST] Re: Source impedance?

["Doug Brooks" <doug@xxxxxxxxxx>]

My opinion is that you are correct. Matching the impedance at the front end 
would be important, of course, if you wanted to maximize the transfer of 
power to the load. But if power is not an issue, and if crosstalk is not an 
issue, and assuming zero trace lengths within the source, then source 
impedance is not a factor.

Doug Brooks


At 03:38 PM 1/8/2002 -0700, David Kaiser wrote:

>Theory question. Assume perfect world with no parasitics.
>
>If a 50 Ohm trace on a board is terminated with a 50 Ohm resistor at the end
>of the trace, is there any advantage in terms of SI
>to driving the trace with a source that has 50 Ohm output impedance compared
>to a source with 10 or 20 Ohms of output impedance?
>
>It seems to me that the only thing the series source impedance would do to a
>50 Ohm line that is terminated with a 50 Ohm resistive load would be to
>divide the amplitude in half without improving the signal integrity.
>Correct?
>
>David
>

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