[time-nuts] Low noise voltage regulators

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Feb 24 22:22:02 UTC 2010


You can improve the performance of the LM723 if one substitutes an LM329 
for the internal reference biased from the regulator output.
The trick is to use the internal reference for startup and decouple it 
with a diode or similar once the LM329 achieves its nominal output.

Currently, there appear to be 2 variants of the LM723 one (made by 
National) that uses a noisy bandgap reference and another variant that 
actually uses a quieter zener reference.

Bruce

Brooke Clarke wrote:
> Hi neville:
>
> My old Gibbs rack mount 5 MHz standard used the LM723 linear 
> regulator.  I believe it's one of the lowest noise regulators you can 
> use.
> http://www.national.com/mpf/LM/LM723.html#Overview
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
>
>
> Neville Michie wrote:
>> Hi,
>> 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 
>> temperature.
>> 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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>
>
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