Charles et al, http://www.pst.netii.net/spice/ripple/ripple.htm
holds some interesting spice simulations of various refinement techniques. Best regards Ulrich Bangert > -----Ursprungliche Nachricht----- > Von: [email protected] > [mailto:[email protected]] Im Auftrag von Charles P. > Steinmetz > Gesendet: Freitag, 1. Februar 2013 18:35 > An: Discussion of precise time and frequency measurement > Betreff: Re: [time-nuts] Low noise power supplies? > > > Joe wrote: > > >Back when I was in product engineering there was a VCO design that > >used a "superfilter" circuit. It consisted of a pass transistor and > >a filter cap from base to ground. The gain of the transistor > >multiplied the effective capacitance. I have not seen this > configuration since. > > They are often called "capacitance multipliers" and are popular with > (among others) audio designers as low-noise supplies for low-level > circuits (moving coil head amps, RIAA stages, etc.). They are best > used following an active regulator. If the capacitor is > electrolytic, it needs to be chosen very carefully so that leakage > current noise doesn't spoil the effort. Also, it is best to use a > voltage divider on the base to give the transistor a bit of headroom > (i.e., base voltage should be a volt or so lower than collector > voltage, not the same as the collector voltage as happens when there > is just a pull-up resistor on the base). > > Best regards, > > Charles > > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
