If you read a little further you should find that there is a frequency dependency. Tom has pointed out that for frequencies <1kHz current takes the path of least resistance. For frequencies >10kHz current takes the path of least reactance. You will find this in is presentation on EMC Principles on the RMCEMC website. Go to http://www.ieee.org/rmcemc and look for our October presentation. Best Regards Charles Grasso Senior Compliance Engineer Echostar Communications Corp. Tel: 303-706-5467 Fax: 303-799-6222 Cell: 303-204-2974 Email: charles.grasso@xxxxxxxxxxxx; Email Alternate: chasgrasso@xxxxxxxx -----Original Message----- From: Darshan Mehta [mailto:darshanmehta2k@xxxxxxxxx] Sent: Wednesday, December 01, 2004 8:01 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Power and Ground Plane area Hello Everybody, I was reading one of the IEEE paper on topic "EMC Analysis" by Dr. Tom Van. He says that Return current takes the least impedance path. If the signal speed is 1 KHz, there is no need of Power or Ground Plane because even if you have Power Plane, the return current will not effectively utilize the plane. So my question is, how we should decide at what signal speed we should use Plane area for Power and Ground. Is there is any specific formula for that. Thanks. Best Regards Darshan Mehta --------------------------------- Do you Yahoo!? Meet the all-new My Yahoo! - Try it today! ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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