[time-nuts] Low noise voltage regulators

[Bruce Griffiths]

The LM723 from STMicroelectronics still uses a buried zener and its 
typical noise specs about 4x less noisy than the National part.
With an LM329 4reference it should be about 2x quieter than the ST version.

Bruce

Didier Juges wrote:
> The original 723 (I remember the uA723 made by Fairchild, I still have a couple of 30 year old parts here) had a buried Zener and was considered pretty quiet at the time.
>
> I am not sure how it would compare with today's low noise references, but the last time I checked, it was pretty good, even more so when considering the voltage is 6 or 7 volts, compared to typically much less for a modern reference.
>
> Didier
>
> ------------------------ Sent from my BlackBerry Wireless thingy while I do other things...
>
> -----Original Message-----
> From: Bruce Griffiths<bruce.griffiths at xtra.co.nz>
> Date: Thu, 25 Feb 2010 11:22:02
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Subject: Re: [time-nuts] Low noise voltage regulators
>
> 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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>
>
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