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Lowest noise power supply

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drwho9437:
Most switching bench supplies are very noisy. Even supplies with digital monitoring can have unwanted noise. I remember in my first group we only used power supplies with panel meters.

For people who have done ultra-low noise measurements (particularly 1/f performance < 100 Hz); what PSUs have you found the best?

<350 uVrms for sure 20 MHz seem easy. How about 10 uVRMS with 1 nV/rHz down to 5 Hz or something?

What is out there?

mawyatt:
Long ago when working below 10Hz we employed various type batteries for our low current , noise and frequency use.

Best

Vgkid:
Are you looking at new , or old.
For new Stanford Research DC205 have low noise.
For used HP precision supplies , and certain  Power Designs precision models are the way to go.
For the lowest noise...batteries , and there can still be noise.

NiHaoMike:

David Hess:
I just build my own when needed.  Enclosing a regulator within the feedback loop of a precision low noise operational amplifier and using a low noise reference will easily achieve the noise of the reference alone while keeping the failsafe operation of the regulator.  Lower noise then requires summing the output of multiple low noise references.  Flicker noise is dominated by the reference as well, so using a chopper stabilized operational amplifier provides only marginal benefit.

Using battery power avoids noise from common mode capacitive coupling across the transformer of an off-line power supply, however some low noise off-line power supplies have good enough electrostatic shielding in their transformer and design to also be suitable.

Typical parts are any 3 terminal regulator, a precision low noise operational amplifier like the LT1001, and a low noise reference like the LM329.  Buried zener reference have lower noise than bandgap references when their higher reference voltage is considered.

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