Extreme noob electronic question

[Tony Hardie-Bick]

On 18/01/13 14:03, Marc Nostromo [M-.-n] wrote:
> I'm still slightly confused between polarized versus non polarised capacitors :)
>
> I'm going to need a voltage regulator to bring down 9v to 5v with a
> LM7805 using this rough schematics
>
> http://snesdev.antihero.org/wp-content/uploads/2008/03/lm7805.gif
>
> I undestand the capacitors are used to stabilize the ac changes in the
> DC supply. Does that mean I can't use polarised caps ?
>
> Because my impression is that the voltage will no matter what be
> higher than the ground so polarity should not get in the way.

yeah - your understanding is correct.

an electrolytic (polarised) capacitor requires a certain amount of
voltage across it so its internal insulating layer remains intact. If
you reverse the polarity, this layer gets eroded, and the thing starts
conducting. So, as long as you have correct polarity, and preferably
some voltage, then it's okay.

in an analogue circuit, you can let it go negative sometimes, but only
if either a) you are bad at circuit design or b) you like your filters
sounding rough

lol

Tony (HB)