signal pickoff

Right. Most surface mount resistors are made on 20 mil alumina, with about the same aspect ratio, so their capacitance (and their thermal resistance, and power dissipation capability [1]) is independent of size.

[1] assuming you heat sink the end caps ============================================================

For completeness, was the mistake made when doing the calculation, or when typing up the post? Is the estimate for a 1206 SMD resistor 30 fF and you just happened to type SiO2 instead of Al2O3, or really 9.7/3.9 times that,

75 fF? Interesting that one is about 50% below the measured value, and the other about 50% high; I would predict that the estimate would be low due to field leakage around the sides. Anyway, just pedantically curious.

----- Regards, Carl Ijames

I meant Al2O3, honest. The capacitance values are right. I measured several resistor values. Details if how I went about it are at: . Gosh, that's five years ago, already.

Jeroen Belleman

Don't stop now; you're on a roll.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Good for 30kV then! So your 1200 volts is no problem :)

--

John Devereux

Of course. However, as you know, I build a lot of low-level stuff where the noise of high- value resistors is as inconvenient as their slowness. Finding ways round it is a fun problem, even better than Fields's 555s. ;)

Cheers

Phil Hobbs