[sdiy] capacitor voltage ratings

[harrybissell]

I have heard of voltage modulation of capacitance... otoh iirc
it was in Ceramic caps of crappy dielectric (like X7R or Z5U).

It might happen with some electrolytics as well, but it is nowhere
near what you are describing.  It would be a small fraction of the total
capacitor tolerance... maybe a 1% effect and nothing to worry about
unless you are using them in audio coupling applications where...

(as you said...)

a film cap would be a better choice anyway.

H^) harry

John Henson wrote:

> To an extent this is true.
> You can (and probably should) replace 16V caps with 25V ones if your voltage
> rails are + & - 12V or 15V.
> The downside is that the capacitance of electrolytics is dependent on the
> voltage across them.
> If memory serves, electrolytics only come close to their specified
> capacitance if the voltage across them is within 75 or 80% of their
> specified voltage.
> Thus, space considerations aside, putting 100V or higher Caps across synth
> type power supplies is largely self defeating.
> This problem does not occur with film type caps.
> Regards
> John Henson
>
> ----- Original Message -----
> From: <Rafael_Cohen at prusec.com>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Friday, May 20, 2005 8:20 PM
> Subject: [sdiy] capacitor voltage ratings
>
> >
> > Hey everyone,
> > Yet another newbie question here.
> > I am curious about the voltage ratings on capacitors.  I was buying some
> > from www.Jameco.com earlier today and I was trying to figure out the
> > dirrefences in price and the differences between the different
> products....
> > If I have a previous circuit that I am trying to copy and the old one uses
> > 100uF caps at 16V can I substitute 25V?  50V?  Why are some cheaper than
> > others?
> >
> > Also, in the CGS parts lists (soon to build my Steiner VCF), some of the
> > modules list caps at a particular voltage.  If I am substituting, is it
> > irrelevant as long as it is a higher value than the given specifications?
> >
> > Thanks for any info...
> >
> >
> > Rafael
> >
> >
> >