[time-nuts] Low noise voltage regulators

Bob Camp lists at rtty.us
Wed Feb 24 22:15:35 UTC 2010


Since the LPRO has a "noisy" 3 terminal regulator inside it, making the
outside voltage quiet (as in noise density) probably will not help much.

Keeping the voltage *stable* will indeed help things. I think you need a
high stability linear regulator rather than a low noise one.

One other thing to think about is line isolation at both audio and RF. Most
regulators have poor isolation above a few 10's of KHz. 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Neville Michie
Sent: Wednesday, February 24, 2010 4:57 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Low noise voltage regulators

I remember a reference, probably by Bruce, that LEDS provide a low  
noise voltage reference.
I am proposing to build a voltage regulator for a thermally  
controlled LPRO rubidium oscillator,
with the voltage regulator being mounted on the 0.5 inch thick  
aluminium heat sink plate.
The LEDS would also be mounted on the plate, which has controlled  
The LPRO has internal voltage regulation, and by running it at ~40C  
and 18Volts, the thermal
flux within the unit is minimised as is the power demand.
What I want to know is if a LM317 running on a stack of LEDs driven  
by the LM317 output
would provide a low noise power source? What would be better?

cheers, Neville Michie

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