Assuming we are looking at a model like this driver >txline>cap>gnd You can look at this from the two boundary conditions first. With a "large" value cap, this looks like a shorted line. The first thing that happens is there is a large negative reflection and then the line stabilizes with zero voltage at the far end. Then the cap charges based on the RC time constant between the output impedance of the driver and the value of the cap. With a "small" cap, the cap charges quickly, it looks like an open line, there is a 100% positive reflection, and the voltage at the far end of the line rises to the open ended driver voltage. With a cap value "in between," these two effects will combine, based on the relative values. Exactly what happens depends on the values chosen for the driver output impedance, the Zo of the line, and the cap value. This can be modeled pretty easily with a tool like Hyperlynx. Doug Brooks ------------------------------------------------------------------ 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