[time-nuts] Low noise power supplies?

[Bob Camp]

Hi

The circuit I described, is (as stated) quiet down to 100 Hz. It's 3 db bandwidth is well below 10 Hz with the 47 uF cap. If you need it quiet down to 10 Hz or 0.000000001 Hz, you will need to buy a few more caps. It's still not rocket science.

For most OCXO or atomic standard testing applications out there, 10 Hz is low enough. 

Bob

On Jan 31, 2013, at 9:41 PM, Charles P. Steinmetz <charles_steinmetz at lavabit.com> wrote:

> Bob wrote:
> 
>> An AD 797, a couple of metal film resistors, and a fairly large (say 47 uf) plastic cap work pretty well.
> 
> The band from 10 Hz down to 0.1 or 0.01 Hz is generally important when testing oscillators.  To keep the 797 input noise density below a few nV per root Hz, the terminations must have very low resistance.  With such low resistance, a 47 uF cap won't even get you to 10 Hz, much less 0.1 or 0.01 Hz.
> 
> One more thought: Many oscillators have internal regulators that are not nearly as good as what you can build.  No sense using an external supply with 5 nV per root Hz noise density if it will be re-regulated inside the oscillator by a circuit that has a noise density of 250 nV per root Hz.
> 
> Best regards,
> 
> Charles
> 
> 
> 
> 
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