At high frequencies (for arugument say >500MHz), the via impedance to the "capacitor planes" limits its usefulness. For those frequencies, a close capacitor, appropriately sized, makes lots of difference. I was working on a 900MHz design at "another company" where putting the power cap on the leads of the part instead of the PCB made a definite performance difference. Of course, that was in a lab environment so we could do crazy things like that. ;) I've also used via inductance for filtering by resonating it with a cap. It surely wasn't a high quality filter, but it helped. =20 -- Mark Randol, Engineer Intel Corporation, 5000 W Chandler Blvd, MS CH6-451, Chandler, AZ 85226 480-554-3025 (voice), 480-552-8946 (FAX) mark.d.randol@xxxxxxxxx ------------------------------------------------------------------ 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