I tried your idea of using a diode, 200 ohm resistor, and capacitor and it does work. I'm not sure what kind of diode I used, I just picked an old unmarked one from my parts bin. I did not have a really small capacitor, so again I used an old disk capacitor from my parts bin that measured about 20pF. I tested it at frequencies from 1MHz to 80MHz using sine waves. I noticed some AC ripple on the output that increased with frequency. I was wondering if it would work to parallel a smaller capacitor, like your suggested 1pF, to decrease the ripple at higher frequencies. I know the total capacitance would increase, but my thought is that the small cap would charge quicker and thus reduce the ripple at higher frequencies while the larger cap would hold its charge longer to handle lower frequencies. Does that make sense?
