[SI-LIST] Re: Crystal Oscillator

Hi Raymond,
    Thanks for the detailed explanation. As you quoted
">When operated at parallel resonance the quartz resoantor 
contributes
>180 degrees phase shift."
    Could you Pl. explain how the quartz resoantor  contributes 
180 degree phase shift?

Thanks/-
Pankaj


On Sat, 26 Jul 2003 Ray Anderson wrote :
>
>Pankaj-
>
>A quartz crystal resonator has two resonant modes, series and 
>parallel.
>(The series resonant frequency is (to a first order 
>approximation)
>determined by the series combination of the motional inductance 
>and
>motional capacitance of the quartz crystal.
>
>The parallel resonant frequency is determined by the series 
>connection
>of the motional inductance and motional capacitance in parallel 
>with
>the shunt holder capacitance. The series and parallel frequencies 
>are
>very close to each other, typically separated by only a few 
>kilohertz.
>
>Also note that when operated in the series resonant mode, the 
>quartz
>resonator contributes ZERO degrees phase shift at resonance. 
>When
>operated at parallel resonance the quartz resoantor contributes
>180 degrees phase shift.
>
>So an oscillator whose active element contributes 180 degrees 
>phase
>shift (perhaps a single inverter) may be used at the parallel 
>resonant
>frequency of the quartz resonator to sustain oscillation. (180 + 
>180 =
>0 degrees or positive feedback).
>
>If your active elements contribute 0 degrees phase shift (say, 
>two
>invertors), then the quartz resonator will operate in the series 
>resonant
>mode (with zero degrees phase shift contributed by the crystal) 
>to
>sustain oscillation at the series resonant frequency.
>
>Note that capacitive loading by the oscillator circuit can 
>'pull'
>the actual frequency of oscillation slightly, and may 
>contribute
>a small amount of phase shift that may cause the oscillator to 
>actually
>operate slightly off the series or parallel resonant frequencies 
>of
>the unloaded quartz resonator.
>
>I hope this explanation helps out.
>
>Ray Anderson
>Staff SI Engineer
>Sun Microsystems Inc.
>
>
> >
> >Hi Raymond,
> >   I have some querry about crystal oscillator at parallel 
>resonance. The
> >reason, I am asking you personally is because I posted the same 
>question
> >in SI list, but unfortunately didn't get any response. Your 
>help will be
> >really appreciated.
> >   I understand in parallel resonance mode 180 degree(infact 
> >180)
> >phase shift comes from inverter. Also, other 180 degree phase 
>shift will
> >come from crystal and load. Now, crystal is modelled as 
>inductor above
> >series resonance. That means, we are having inductor and 
>capacitor, which
> >acts like tank circuit. But, tank circuit will give 0 degree 
>phase shift.
> >So, I am wondering how we are getting the remaining 180 degree 
>phase shift?
> >  Any insight will be great help to me. Also, please forward me 
>some
> >good links.
> >
> >  Thanks in Advance.
> >
> >Pankaj Kumar
> >IO Design Engineer
> >ARTISAN COMPONENTS, INC.
> >
> >www.artisan.com
> >
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject 
>field
>
>or to administer your membership from a web page, go to:
>http://www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List archives are viewable at:
>               http://www.freelists.org/archives/si-list
>or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>
>



___________________________________________________
Download the hottest & happening ringtones here!
OR SMS: Top tone to 7333
Click here now: 
http://sms.rediff.com/cgi-bin/ringtone/ringhome.pl


------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: