[time-nuts] Low noise power supplies?

[Bob Camp]

Hi

A very common way to check one is to use the HP 3561 off of the old 3048
phase noise test set. With a simple op amp based preamp you can easily get
down below 3 nv / sqrt(Hz). With more exotic amps you can get well below
that. 

Volts over a bandwidth really don't tell the story very well. In the popcorn
noise region, you don't have much choice. Once you get past that PSD is very
much the right way to go. 

For some numbers once you are out of the popcorn / flicker noise region:

1 nV / sqrt(Hz) = about as quiet as it's worth getting ever.
10 nV / sqrt(Hz) = good enough for anything you are likely to be doing
100 nV / sqrt(Hz) = noisy enough to begin to bother you in some cases
1uV / sqrt(Hz) = pretty awful.   

As always, it really depends on what you are doing. A microprocessor will
not be bothered much at all by a relatively noisy supply. 

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Burt I. Weiner
Sent: Thursday, January 31, 2013 12:08 PM
To: time-nuts at febo.com
Subject: [time-nuts] Low noise power supplies?

Gang,

I'm following this thread with great interest, but, just for my own 
reference, what is considered low power supply noise?  Can you give 
me some numbers and over what bandwidth?

Thanks,

Burt, K6OQK



>         <time-nuts at febo.com>
>Subject: Re: [time-nuts] Low noise power supplies?
>
>
>Hi
>
>To answer the original question - Power Design makes some pretty quiet
bench
>supplies. If you are doing low noise testing, batteries often will let you
>get rid of one more ground loop. Even well built power supplies are not as
>well line isolated as a battery.
>
>Bob

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net
www.biwa.cc
K6OQK 

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