The sawtooth, in the comparator I built, it makes an output signal that almost looks like the signal seen driving a pair of mosfets in a class-d amp.

No good... Mostly from the noise that isn't from the opamps. It is from the optical side of the signal. The noise voltage is small, but still, it doesn't work well. Even with hysteresis adjustable with diodes and 10k or 1k pot.

This is why I love electronics, the challenge. But dang, it can really push the minds limit sometimes.