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Re: gEDA-user: capacitors

The step from an electro to high quality high stability is a big one.
If the OP wants reasonable advice, describing the application a bit is probabably a good idea.

Whats important to you:
voltage? frequency range? temp range? current in the capacitor,
space available, capacitance linearity with applied voltage,
leakage, stability over time, cost, microphonics.... its a long list. Probably only one or two really matter in any specific app.

The only case where a non-polarized capacitor is not a better replacement for a polarized one (ie an electro) is if size or cost is significant. Electros are high-capacitance-density, cheap and cruddy compared to most anything else.


Bill Sloman wrote: 
At 02:58 15-2-2006, you wrote:

Im wondering what i can use instead of Electrolytic capacitors, what is high quality high stability polarised capacitor at value of 0.01uf

any ideas pls


Hi Marc - the right user-group for this sort of question is sci.electronics.basics. The answer is, that for a capacitance as low as 0.01uF you don't need to bother using a polarised electrolytic capacitor at all - metallised film capacitors are much better capacitors. If you want particularly high quality, go for polypropylene film - Farnell list a 0.01uF (10nF) +/-1% part with 160V DC (100V AC) maximum working voltage under order code 303-8543 for 1.3 euro each.

If you were prepared to use an electrolytic for the job, a much cheaper ceramic disk or chip part would presumably be perfectly adequate (and better at very high frequencies). Polyester metalised film capacitors can also be pretty cheap.

If you are primarily interested in temperature stability, polystyrene at 110ppm/C is better than polypropylene at -200ppm/C, and polyphenylene sulphide is better still
"from -55°C to +85°C, PPS is virtually flat at 7 ppm/°C" but I've only used it in surface mount capacitors. RS Components stock PPS parts.

Bill Sloman