[time-nuts] Low noise power supplies?

[Max Robinson]

You haven't seen it used because it doesn't work very well.  It appeared in 
a few pieces of Heathkit equipment but I don't think HP or Tek used it at 
all.  Any AC component of base to collector voltage has a small but definite 
effect on Vbe which transfers voltage in the reverse direction from 
collector to emitter even though the base is held at AC ground.  A three 
terminal regulator does a better job of suppressing ripple from a power 
supply.

Regulators use a zener diode as the reference and there are circuits in 
which a zener is used as a noise source.  What does that tell you?  The 
quietest power supply is an analog regulator followed by one or more RC 
filter sections.  The inductor in an LC filter is likely to pick up more hum 
and noise than it filters out.  My presumption is that a low noise power 
supply is likely to be providing a small amount of power to the load and 
load regulation is probably not a problem.

Regards.

Max.  K 4 O DS.

Email: max at maxsmusicplace.com

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----- Original Message ----- 
From: "Joe Leikhim" <jleikhim at leikhim.com>
To: <time-nuts at febo.com>
Sent: Thursday, January 31, 2013 2:39 PM
Subject: [time-nuts] Low noise power supplies?


> 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.
>
> -- 
> Joe Leikhim
>
>
> Leikhim and Associates
>
> Communications Consultants
>
> Oviedo, Florida
>
> JLeikhim at Leikhim.com
>
> 407-982-0446
>
> WWW.LEIKHIM.COM
>
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