[time-nuts] Low noise power supplies?
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Thu Jan 31 21:41:39 EST 2013
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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