Think of the transmission line's characteristic impedance as either: - the impedance of a theoretically infinitely long transmission line - the impedance of a line seen by a signal before the reflection returns from the opposite end or other discontinuities on the way By definition (aka in theory), terminating the transmission line using it's characteristic impedance is equivalent to the first. In practice it lowers the effects of the second, excepting other discontinuities. -- Mark Randol, RF Evaluation & Application Engineer -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx on behalf of Karthik Raj Sent: Wed 5/31/2006 8:12 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Terminations Query =20 Hi, I have a basic query on the parallel termination techniques that are widely used. When a transmission line is terminated (lets assume a 50ohm parallel termination) we tend to match the Parallel termination resistance with the Trace Impedence. Instead shouldn't we match the Termination resistance to Source impedence of the driver + Trace Impedence, since they both are in series? Please forgive me if i am sounding stupid. Thanks, Karthik ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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