Homebrew PCBs

Im curious how do big capacitors have internal inductance. If they
have inductance wouldnt that cancel some of the capitance that they
have? Are you talking about the leakage current? This would be the
only thing that passed dc. 

Regards
Dennis Waggoner


--- In Homebrew_PCBs@yahoogroups.com, "John Popelish" <jpopelish@...>
wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "sbdwag" <sbdwag@> wrote:
> >
> > Len
> > 
> > I am really just a grasshopper but the power supply circuit filters
> > well and is very stable.
> > 
> > http://www.wagsterstuff.com/photos/pssch.jpg
> > http://www.wagsterstuff.com/photos/pspeg.jpg
> 
> A point you might keep in mind is that big electrolytic capacitors
> have quite a bit of internal inductance, so it isn't so important that
> they have very little trace length between them and something that
> needs to be close to capacitance.  Getting them close won't help,
much.  
> 
> But the regulators have best stability when the three small capacitors
> connected to them all hit ground at the same node, and when there is
> very low trace inductance between them and the regulator.  So the .22,
> 10 and 1 uf caps should be tucked in as close to the regulators as you
> can fit them, with all three sharing a very short ground branch.  
> 
> Since the big electrolytics can be further away and still work fine,
> and since they are temperature sensitive and they generate internal
> heat from ripple current, and the regulators get hot, it is a good
> idea to have them located a fair distance from the regulators, and
> with a bit of air space all around to keep them cool.
>