FreeLists / si-list / [SI-LIST] Re: Parallel Resonance of crystall oscillator

[Lieby David <DLieby@xxxxxxxxxx>]

Hi,

I believe that in a crystal circuit, the crystal sees 
the two capacitance in series.  The ground plane, 
or whatever, is merely a wire connecting the two caps.  
Like any good tank circuit, sort of floating in free 
space, the ends of the inductor are always out of phase.
This of course only if it is being driven and loaded
correctly.

I have seen many cases where people do not look at
the caps as being in series with some hilarious and
embarrassing results.

dav0
David Lieby 
Acuson, a Siemens Company

Bi Han wrote:
> 
> The phase shift is most mentioned in ring oscillators.
> 
>  Parthasarathy Sampath <parthsv@xxxxxxxxx> wrote:
> Hi all,
> I have a question regarding crystall oscillator
> operating at parallel resonance.
> At parallel resonance, the impedance offered by
> series resonant ckt within crystal oscillator is
> inductive. This inductive reactance is cancelled by
> the capacitive reactance offered by parallel
> capacitance in the crystall oscillator and the load
> capacitance. So there should not be any phase in the
> circuit since the reactances get cancelled. However a
> lot of articles say load capacitance provide a phase
> shift of 180 in order to oscillate in closed loop.
> Since the load capacitance is included in the parallel
> resonance to cancel inductive reactance, how can it
> contribute 180 degress phase shift.
> 
> Thanks in advance,
> Partha

-- 
dav0
David Lieby, SI Engineering
Acuson Corporation, a Siemens Company
1230 Shorebird Way
Mountain View, CA 94043

Building E
P.O. Box 7393
Mountain View, Ca 94039-7393
(650)694-5030
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