If we use a little bit more imagination. Suppose you have a 50 ohm control impedance source in a bi-directional point to point bus. When are done driving, turn on the high or low side constantly and you become a receiver terminator. turn on half high/ half low you become a CTT terminator. Very convenient. Now if both side drive at the same time, you've got a very nice simultaneously bi-directional I/O. Very neat. -----Original Message----- From: David Kaiser [mailto:david.kaiser@xxxxxxxxxx] Sent: Tuesday, January 08, 2002 2:39 PM To: 'si-list@xxxxxxxxxxxxx' Subject: [SI-LIST] Source impedance? 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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu