> Can someone please tell me the use and the benefit of a varactor diode in > having an automatically programmable clock delay. And why exactly varactor > diodes and not other diode? Do you know what the varactor diode is doing? The purpose of the diode is to provide an electrically adjustable delay, by way of the diode's voltage- dependent reverse-bias capacitance. In fact many people would call it a varactor diode even if it wasn't one designed specifically for that purpose. i.e., if you used some other type of diode there, it would be called a "varactor diode" anyway, because of how it functions in that circuit. (Just as a "clamp diode" doesn't need to be one that was designed as a clamp diode.) Varactor diodes that are designed as such are optimized for use as an electrically controlled capacitance. Many have a controlled doping profile which gives them a particular C(V) characteristic that may be desired, and/or a wider max/min capacitance range (wider tuning range when used in tuned circuits). Yes, you could use some other type of diode instead, like a small signal switching diode (and such diodes have been used as varactor diodes) but it might not work as well as a diode that was designed to be a varactor diode. Regards, Andy ------------------------------------------------------------------ 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