[time-nuts] Low noise power supplies?

Ulrich Bangert 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.

Best regards
Ulrich Bangert

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] 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
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