On Mon, Oct 19, 2009 at 5:27 PM, Dan McMahill <[email protected]> wrote: > my recent experiences are more in line with Larry's. Most C for a given > package and voltage seems to be the best meaning that above resonance it > is no worse than smaller capacitance value devices and below resonance > it is better. And yes, this seems to fly in the face of what has been > recommended in the past. I've not done any careful measurements of > older technology bypass caps but I wonder if this is one of those > "rules" which became obsolete 15-20 years ago and no one noticed... > > -Dan
I have done some testing of various passives (mostly 0402) and came to the conclusion. I tested both shunt and series capacitors on a 50 ohm transmission line with a VNA. What was most interesting to me was that the large value capacitors performed better as series coupling caps than the small ones. The single layer caps in the 1 to 100 pF range frequently had parallel resonances in the 10 to 30 GHz range. Most of the multilayer caps (10 nF to 1 uF) performed well to at least 30 GHz. I like to use 3 terminal feedthrough capacitors when I am concerned about frequencies > 1 GHz getting on the power supply. Darrell Harmon _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
