[time-nuts] Low Additive Phase Noise 10 MHz Amps

Richard (Rick) Karlquist richard at karlquist.com
Mon Nov 24 00:53:38 EST 2014

I did some checking around for low noise buffer amps earlier
this year.  They needed to have 200 MHz bandwidth, so this
isn't directly applicable to 10 MHz.  I also needed isolation.
About the only information in print is from the usual suspects
at NIST.  They wrote a series of papers taking a fairly classic
discrete design and refining it.  Check FCS proceedings.  My
idea was to take ideas from 10 MHz and extend them to 200 MHz.
I didn't see any really profound ideas in the NIST papers.
There is a reproducibility problem because the original discrete
devices may not be available, or NIST might have used special
hand picked devices.

BTW, I cringe when I see the term "additive phase noise".
Phase noise, as all time nuts know, is NOT ADDITIVE NOISE,
as in AWGN.  It is multiplicative.  The correct term, IMHO,
is "residual phase noise".  What additive noise refers to
is the classic noise figure type noise involving small signals.
Again, as all time nuts know, low NF is necessary but not
sufficient for low phase noise.

Rick Karlquist N6RK

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