Haha, I try to explain why "parallel mode" is not a good name. Now you ask me for arguments why it should be called that?
Also the "absence" of visible LC's is not the reason. That would be a reason to deny series resonance as well ;-)
No, please have a look at my last response to Joel's post.
Cheers,
Joop
The frequency uncertainty is actually very similar to crystals in a series resonant oscillator. If you look at my simulation you will see the phase change around the resonance point is just as steep in all circuits. Manufacturers simply specify a load capacitance to obtain the advertised crystal frequency. Some mention this as a "parallel" specification, some leave that part out. Because really it does not matter what circuit you use as long as the load capacitance in the oscillator matches the datasheet.
So the uncertainty can be specified nicely for a certain amount of ppm depending on how reproducably the manufacturing process is.
Stability is another matter and has got more to do with drive level and stability of the effective load capacitance. My last crystal oscillator was a single transistor Butler oscillator to build a 10MHz frequency reference. Although I have doubts about the name. I have seen many different oscillator types that all claim the name Butler. It was modified somewhat during simulation to have both a low drive level and low load impedance. The result really was a pleasent surprise. From the first reading after power-on until the next 15 minutes, the change in frequency was less than 0.5Hz. This was before I added the varactor section to lock it to a GPS module. The varactor has a substantial tempco (well you can quickly get used to sub-Hz drift..). But the 10KHz GPS module will keep it locked nicely. By the way, this was an ordinary 10MHz computer crystal from a nearby shop, so not a special tailor made article.
Joop
A fourth section has been added. Its a Pierce circuit with a additional series inductor that put's the operating point back to the crystals series resonance frequency.
Compare the two cursors of the Pierce/180-degree and Series/0-degree frequencies.
Joop
I don't
all that
a result
ge to be
That is precisely why I don't have a graduate degree yet. I'm still=20 evaluating the pro's and con's for various programs of study.=20
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