A cap can be considered as a frequency dependant resistor. High freqs
can pass and low freqs can't.
Have a look at this picture:
http://www.elecdesign.com/Files/29/1478/Figure_01.gifThe +5V offset can be considered a very, very low frequency (f->0).
On the other hand you can construct a lp filter, by "shortening" the
high frequencies through a cap. Then you have to take the signal from
before the cap, because the low frequencies stay there.
> hehe i'm even more new to this stuff and i really don't understand how
> running AC signal through a cap eliminates the DC offset... shouldn't
> that eliminate the high frequencies (and thus the oscillation)?
>
> jure