On Wed, 21 Jan 2004, Martin McCormick wrote:

>         Assuming that the RC time constant of the low-pass filter is
> long enough to smooth out the PWM ripple, is the relationship between
> output voltage and duty cycle a linear percentage of the voltage based
> on the percentage of the duty cycle?

Yes.

Long answer:

http://www.dattalo.com/technical/theory/sqwave.html

(a page you'll appreciate for no other reason than the fact that the art
is all ASCII! :)

If you look at a square wave in the frequency domain, it's DC component
is the duty cycle. So, if your RC filter can truly suppress the higher
frequencies, then the DC voltage will be exactly proportional to duty
cycle.

Scott

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