[time-nuts] Low noise power supplies

[Charles Steinmetz]

Chris wrote:

>Just practical question.. How would one measure noise at this 
>level?  If I were evaluate this what would I need?

Generally, one starts with an extremely low noise amplifier.  Note 
that isolating the very low frequency AC components from the DC 
component is a substantial difficulty (we are interested in AC noise 
well below 1 Hz).  For example:

<http://www.edn.com/design/analog/4313942/Characterizing-noise-in-high-performance-voltage-reference-ICs>

See also:

Linear Technology Application Notes 124 and 83

Bruno Neri, et al., Ultra Low-Noise Preamplifier for Low-Frequency 
Noise Measurements in Electron Devices, IEEE Transactions On 
Instrumentation And Measurement, Vol. 40. No. I. February 1991

Felix A. Levinzon, Ultra-Low-Noise High-Input Impedance Amplifier for 
Low-Frequency Measurement Applications, IEEE Transactions On Circuits 
And Systems - I: Regular Papers, Vol. 55, No. 7, August 2008

Some spectrum analyzers with cross-correlation capabilities can get 
you in the ballpark if you let them average long enough, although you 
are much better off if you use an ELN amplifier there, too.

Best regards,

Charles