[quote author="SSLtech"]I did breadboard a
simple working unit some time ago, but never fully developed it. It used readily-available devices, -I'd love to see what you made of the sketch, Brad...
-There's probably a dozen stupid things that I did wrong. -PRR did make some very helpful observations, and greatly changes my mental approach to how well (or rather,
not well) op-amps reject high-frequency schmutz, but I've not revisited that sketch for some time.
Keith[/quote]
I see that thread started before my time here, but also that I still managed to stick my oar in late in the game.
Looking it over now, it seems fine. As usual PRR's comments are well-considered.
Probably a few things I would do a little differently, as among other things I've never been a big fan of the 555, and I'd have a teensy bit of hysteresis applied around the 319, etc. etc. There might be a first-order compensation of the FET gate-channel-coupled switching charge, or some other differential scheme.
Indeed the thread and discussions are good and reminded me of the need to do a thorough job of bandlimiting going into any chopper as well as when coming out of it. Another consideration: in addition to the L-C filtering adjunct suggestion, note that our favorite Sallen-Key filters have some departures from ideal rolloff when you get out to high frequencies. There was some app note/blurb about that recently, and I forget what the author recommended.