[time-nuts] Low noise power supplies?
df6jb at ulrich-bangert.de
Sun Feb 3 07:51:17 EST 2013
Charles et al,
holds some interesting spice simulations of various refinement techniques.
> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Charles P.
> 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,
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> and follow the instructions there.
More information about the time-nuts