[time-nuts] Opamp datasheet noise specs and their relation to phase noise

Stephan Sandenbergh ssandenbergh at gmail.com
Fri Mar 6 06:06:10 EST 2015

Hi All,

Opamp noise is usually specified in it's datasheets as input voltage noise,
V/sqrt(Hz), and input current noise, A/sqrt(Hz) versus frequency, Hz.

Is it possible to estimate the opamp's phase noise at a specific frequency
(say a sinusoid at 10MHz or 100MHz) from these curves?

I'm assuming it can be seen as amplitude noise that is converted to phase
noise. Which in turn make it seem to me that it is dependent on the slope
of the zero-crossing. Meaning it is dependent on signal amplitude and

I've seen some earlier posts where opamp phase noise were measured (thanks
Bruce, thanks Ulrich) and found to be remarkably good.

Another question that could be asked is: What about the phase noise of
those Mini-Circuits RF amplifiers that are only specified by noise figure
(NF), dB?

Can anyone point me to some literature that solves this problem?

Many thanks,


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