Re: gEDA-user: capacitors

[Bill Sloman <bill.sloman@xxxxxxxxx>]

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