Talk:Crystal oscillator

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I think these could all be merged: Timing crystal, Quartz oscillator, Crystal oscillator. If no one objects, I will put them all under Crystal oscillator. And maybe Quartz clock, also. - Omegatron 20:15, May 4, 2004 (UTC)


I guess quartz clock and crystal oscillator should be separate articles. One is a specific application of the other. I will move some material from each to the other, though. - Omegatron 15:16, May 7, 2004 (UTC)

Contents

[edit] mechanical steel filter

From the article: For example, steel is very elastic and has a high speed of sound. It was often used in mechanical filters before quartz.

What is a mechanical filter, how was that one used, what has it to do with oscillators? Thanks, --Abdull 09:32, 19 August 2005 (UTC)

Any resonant system can be used as a component of an oscillator; simply add an amplifier, a feedback loop, and bit of noise to get things rolling.
Atlant 22:09, 27 April 2007 (UTC)

PhysicistQuery 17:24, 20 July 2007 (UTC)The most common mechanical filters were typically cylindrical rods of steel with wide sections and narrow sections along their length. Electroacoustic transducers were used to excite torsional motion, and the wide sections acted as the mass loads and the narrow sections served as the springs. Such filters were analogues of LC filters with all the capacitors grounded.

[edit] Only the quartz crystal or more

Is a crystal oscillator made up only by the single crystal and the feedback/amplifier, or does one still need additional components such as inductors and capacitors? --Abdull 10:14, 19 August 2005 (UTC)

I think all the other components would be considered part of the amplifier. - Omegatron 20:03, August 21, 2005 (UTC)
I agree -- the other components are considered part of the feedback/amplifier.
All the crystal oscillators I've designed (32 KHz to 20 MHz) are made of a single crystal, a single inverter, and 2 capacitors -- a total 4 components. To actually oscillate, some external power source needs to be connected to the inverter -- perhaps a linear regulator connected to a 9 V battery, with 2 more capacitors. No inductors are necessary. --76.209.30.239 06:53, 30 December 2006 (UTC)
It depends on whether you want the purest sine wave or not and whether you want to oscillate on an "overtone". While the crystals are obviously a high Q factor device, the simple crystal+two caps+amp structure doesn't necessarily put out a clean sine wave, free of harmonics. A nice LC tank in the output will help filter out those harmonics. And it can also be tuned to resonate at an overtone of the ordinary frequency that the crystal would otherwise produce.
Atlant 01:14, 31 December 2006 (UTC)

On a similar note, does anyone know what is the exact difference (if any) between a crystal oscillator and a crystal resonator. Are they synonyms, or does one imply additional circuitry or some other difference? Mattopia 09:24, 27 April 2007 (UTC)

To me, a "resonator" is more analagous to "filter" than an "oscillator". A tank circuit, for example, is a resonator. You can certainly use a resonator to make an oscillator, though. (Others' opinions may, of course, vary.)
Atlant 11:47, 27 April 2007 (UTC)
I agree. Crystals are used in electronics for two purposes; generating a signal, and filtering a signal. To generate a signal, the crystal is used in a 'crystal oscillator' circuit. The terminology for a crystal used as a filter is more unsettled. Often the term 'crystal resonator' is used to distinguish a crystal used as a filter. Unfortunately in physics the term 'crystal resonator' sometimes refers to a third use, as a transducer to receive or transmit mechanical vibrations. --ChetvornoTALK 20:25, 10 May 2008 (UTC)


[edit] What does it do exactly?

If a 1MHz crystal oscillator is put in series with a 3v battery will the voltage in the circuit jump from 3v to 0v at a frequency of 1MHz??? Wolfmankurd 17:25, 28 April 2007 (UTC)

Basically, yes, if by "oscillator" you mean the entire circuit with crystal, amplifier, etc. See the above section. — Omegatron 17:49, 28 April 2007 (UTC)
Well it looks like . not one of those 4 pin ones. Wolfmankurd 00:56, 29 April 2007 (UTC)
That's a crystal, not an oscillator. The oscillator is the entire circuit containing a crystal, amplifier, and some other components. — Omegatron 01:29, 29 April 2007 (UTC)
Okay Thank you. Wolfmankurd 11:06, 29 April 2007 (UTC)
This is what I thought as well. Isn't the article title misleading then, in that the component is a crystal but not a crystal oscillator? A crystal oscillator would be the entire circuit that oscillates the signal??

[edit] series resonant oscillator

The Pierce oscillator article says that crystals tuned to a particular "parallel resonance frequency" are tuned using a Pierce oscillator circuit.

So ... what about crystals tuned to a particular "series resonance frequency"? What kind of oscillator circuits ( Category:Oscillators ) resonates at the series resonance frequency? And which one(s) in particular is(are) the one(s) used by crystal manufacturers? --76.209.28.72 05:43, 13 June 2007 (UTC)

PhysicistQuery 17:50, 20 July 2007 (UTC)If you look at the load presented by the oscillator to the crystal under steady-state conditions, it will consist of a negative resistance in series or in parallel with a reactance. The negative resistance will provide the energy needed to overcome the losses in the crystal; the reactance shifts the resonant frequency.

At the present time, the most common configuration for "simple" oscillators is the Pierce configuration, largely because all its elements can be integrated, and it naturally provides an output that is approximately symmetrical between the rails. This makes it convenient for a simple logic buffer to provide a rail-to-rail output suitable for driving digital systems. The reactance of the Pierce oscillator is naturally capacitive, and this is why the crystal is specified with a capacitive load (a pedantic point, but the circuit configuration of a Pierce circuit essentially provides negative impedance and capacitance in series - the "parallel" here refers only to a historic measurement method for the crystal that used a parallel capacitor). The Pierce oscillator can be modified using an external inductor in series with the crystal so that it is operated at series resonance, but this is seldom desirable except when it is necessary to tune the crystal.

An 'ideal' cross-coupled oscillator would ideally operate at series resonance, but in practice stray capacitances are inverted such that the majority of integrated circuit designs provide an inductive load to the crystal. If these oscillators are allowed to limit, the effective series inductance can become quite large.


[edit] Split article?

Shouldn,t this topic be Crystal instead of Crystal oscillator? Thanks.

PhysicistQuery 20:50, 21 July 2007 (UTC)No, this is about the impedance presented by the oscillator circuit to the crystal. If that is now clear, please remove this note. Otherwise, please ask detailed questions.

If someone would start a section on crystal resonators I would be happy to contribute.

I agree. There should be separate articles on "Crystal oscillator" and "Piezoelectric resonator". "Crystal Resonator" should be a redirect to "Piezoelectric resonator". An oscillator is a circuit, while a resonator is a component. The oscillator article can talk about the various circuits, their development and so on. The resonator article can talk about various electrical models, manufacturing, history, various crystal cuts and alternative materials. John Dalton 02:04, 7 August 2007 (UTC)

I was going to suggest the same thing. This article could cover crystal resonators and treat oscillators and filters as two separate cases. -Roger (talk) 23:10, 26 March 2008 (UTC)

[edit] xtal interaction

"Each new distinct crystal source needs to be rigorously justified, since each one introduces new, difficult to debug probabilistic failure modes, due to multiple crystal interactions, into equipment."

Thats a new one on me. What is the failure mode, in what way do the xtals interact? Tabby (talk) 23:39, 22 December 2007 (UTC)

[edit] Crystals and frequency

The entire second paragraph sounds funny to me. If nobody objects, I would like to rewrite the entire thing. There are no frequencies going into our coming out of the crystal. Depending on the implementation of a oscillator circuit (if it uses series or parallel resonance), one usually builds a feedback system with the oscillator in the feedback loop. At the frequency of interest, the impedance of the oscillator becomes very small (series resonance) or very large (parallel resonance). This is in turn used to create a positive feedback, ONLY at those frequencies. The positive feedback amplification will thus build up and sustain an oscillation. Nonlinear effects or amplitude control are usually employed to sustain the oscillation at a certain amplitude and not let it grow too large. If there are no objections during the next week or so, I will rewrite this section. Agunther (talk) 21:43, 7 March 2008 (UTC)

[edit] 20.000 Mhz Use?

Does anyone know what 20MHz crystal oscillators are used for? If so, please add to the table. Thanks. Pi.1415926535 (talk) 15:05, 20 April 2008 (UTC)