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
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