In article , Don Pearce
wrote:
On Sat, 04 Dec 2004 02:17:42 +1100, Patrick Turner
wrote:



Don Pearce wrote:



Teflon's Dielectic Constant is actually quite good, really, go look at
the DC tables.

What on earth is a "good dielectric constant"? And it is nothing to do
with Er that makes teflon poor, it is the charge retention.

The values of proprietary grades like 'Teflon' may vary a bit from one
sample/type to another. However the values I have for PTFE and HDPE are in
the range of epsilon-r 2.2 (HDPE) and 2.1 (PTFE) with both having tan
deltas of about 0.0002 and resistivities around 10^15 Ohmm. Don't know the
charge storage property values, though.

I'd be more concerned with things like noise, distortion, interference,
etc, if both the source and the load have high resistances. i.e. not really
anything to do with the choice of capacitor material. Although that said,
maybe high resistances would make the cap imperfections easier to spot. (?)

Slainte,

Jim

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