[time-nuts] Low noise power supplies?

[Charles P. Steinmetz]

tvb wrote:

>I'll answer the question with anther question -- how does one 
>properly measure power supply noise? Does it boil down to a single 
>number, a couple of key numbers, or is it a plot, or several plots?

There are a number of "standard" ways, some of which have been 
mentioned by others, none of which is all that helpful IMO.

What I find most useful is a plot of noise density vs. frequency 
from, say, 0.1 Hz to as high as you require.  The data should be 
taken and processed with sufficient frequency resolution to show any 
spurs in the band of interest.  It is often helpful to have several 
plots, each covering part of the band of interest, to improve the 
displayed resolution of spurs.

NOTE:  Designing a preamp for collecting the data is far from 
trivial.  Articles have been written about it (see, for example, 
Linear Technology Application Note 124 by Jim Williams 
<www.linear.com/docs/28585>).

Best regards,

Charles