[time-nuts] Gate propagation delay jitter

Bob Paddock bob.paddock at gmail.com
Tue Apr 10 20:46:53 EDT 2007


> I await Bob Paddock's circuit with bated breath.

Found a copy of the circuit I had in mind on line, look at figure #25:

http://www.linear-tech.co.jp/pc/downloadDocument.do?navId=H0,C1,C1155,C1001,C1158,P1442,D1594

That circuit has a few problems, it is also based on ten year old parts.

One of the problems that is easy to fix is related to the bad divider thread.
In a multi-input gate, especially Schmitt Trigger ones, never connect
the inputs together.  There is the obvious problem of more capacitance
on the input, but there is the more subtle difference in switching time
of the inputs within the same gate adding.  Connect the unneeded inputs
to the appropriate logic levels.

Make a current source out of a current feed back op-amp that
has a high slew rate for charging the cap, feeding a fast track&hold.
The A/D itself does not have to be all that fast, as long as there
is little drupe before the sampling cap starts to discharge.

Also check out:

"High-Speed Time-Domain Measurements—Practical Tips for Improvement"

http://www.analog.com/library/analogDialogue/archives/41-03/time_domain.html


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