Sine wave to PWM to sine wave. Output could be improved if the input were even slower, but it's already so slow that it's hard to see the waveform, and output takes a long time to settle as it is. I wish I could change simulation speed. Actually, I wish I knew more kinds of low pass filters. :)
I recall a PWM circuit for radio controlled models which had a pulse period much closer to the rate of change of the input. I guess that's fine when smoothness doesn't matter so much.
