On Fri, 17 Feb 2006 10:21:19 GMT, "W3JDR" wrote:

As a generalization, I think that any circuit that excites the crystal's
series resonant mode will probably outperform a circuit that excites the
parallel resonant mode, because the series resonance is higher Q and is less
affected by external influences.

Joe, a minor issue.

Frerking,"Crystal Oscillator Design and Temperature Compensation" (and
a lot of other folks) says the Q of the crystal is: Q = Xl / R,
where Xl is the motional inductance and R is the ESR. Thus the Q of
the -crystal- is not a function of the mode of operation. Short of
drastically changing R, the crystal Q is unaffected by external
circuitry.

If we speak of overall -circuit- Q then that is a different can of
worms.



Joe
W3JDR


"Tim Wescott" wrote in message
...
JJ wrote:
I am fimilar with Colpitts, Harley, Clapps, Bulter, Piece oscillators?

Which configuration with JFET or BJT would yield the highest performance
and least jitter?

JJ

AFAIK a well-designed Butler oscillator will have the lowest jitter, but I
doubt that you could do the "well designed" part without a lot of bench
work.

Any of the rest (considering a "Clapp" oscillator to mean a crystal
oscillator with rubbering) are good enough for communications work.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Thus the Q of
the -crystal- is not a function of the mode of operation."
------------------------------

Wes,

If you're speaking of the Q of the crystal's inherent series resonance, then
you're right. However, most crystal oscillator circuits that we typically
see in common use operate in the parallel resonant mode, which isn't a
crystal resonance at all. It's the frequency at which the crystal's net
inductive reactance resonates the parallel combination of holder capacitance
and circuit capacitance. As such, it's quite affected by the circuit around
the crystal. When the crystal is operated in a parallel resonant mode as
described, the Q of the overall resonant circuit is much lower than the
crystal's resonant Q.

Joe
W3JDR