[time-nuts] What is a Time-Nut grade Zero Crossing Circuit?

Rick Karlquist richard at karlquist.com
Thu Jul 31 20:59:11 EDT 2008


John Miles wrote:
> Modern ECL parts aren't necessarily that bad compared to the old MECL
> stuff.

My experience goes all the way back to the MECL 1000 series that was
discontinued 30 years ago.  I designed many synthesizers around them
for Zeta Labs.  Every newer family of ECL line receivers has been faster
and had worse phase noise, in my experience.


> For some reason, though, the one circuit I measured (MC100EL16 line
> receiver, driven single-ended) was much quieter at 100 MHz (-150 dBc/Hz
> floor) than at 10 MHz (-140 dBc/Hz floor).  I  need to look into that a
> bit
> further.

This is a very tricky topic.  When measuring the phase noise of a non
sine wave, there are dependencies on how the measurement is done.
What is the measurement bandwidth?  Etc.

In some cases, the noise is mostly common mode, and therefore will
depend on the common mode rejection ratio (if any) of your measurement
circuit.

Rick Karlquist N6RK

Rick Karlquist N6RK




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