[time-nuts] Phase noise & Jitter

Hal Murray hmurray at megapathdsl.net
Tue Apr 29 05:20:48 EDT 2008

> For digital circuits, it would seem that the potential for
> metastability & threshold uncertainty, is reduced when the
> slope-to-noise ratio is optimized. I wonder if this concept is, or can
> be quantified?

I don't think noise hurts or helps metastability.  For every case where it 
might hurt there is the mirror image where it helps.

I would expect a slower rise time to cause more metastability.  Here is the 
way I think about it.  If you have N ns to settle, there is a window in 
voltage that is Y mV wide.  (give or take some statistics)  The signal with 
the faster rise time will spend less time inside that window.

There is probably some limit where making it faster doesn't help any more.

Speaking of rise time...

I'm somewhat looking for a signal generator - digital rather than sine wave.

I'm pretty sure I used an HP box 10-20 years ago that had knobs on the rise 
and fall times as well as frequency and whatever.  Is there some obvious unit 
is should be looking for?  Do they show up on eBay?  ...

These are my opinions, not necessarily my employer's.  I hate spam.

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