Speed of Quartz Oscillators

[name9902]

I was curious as to what was it that determines the speed of a Quartz Oscillator...?

Since they seem to provide the "beat" that controls the CLK wire, in turn controlling the speed of the entire comp

so what determines this speed?

 

[Fullmetal Chocobo]

I believe it is inherent to the crystal. Hence the reason quartz is used for watches so much. The pulsing of crystals is actually a property of the material, so it can't be speed up or slowed down. Not without replacing that crystal with another type, anyway.

 

[Bassyhead]

A quartz oscillator is very similar to a tuning fork. In fact, they're mechanical just like a tuning fork. With a tuning fork, you hit it on something hard and it resonates according to the material, dimensions, etc. A quartz crystal is "hit" with a pulse and it in turn produces a pulse as the crystal flexes back into resting state. This is coupled with a feedback loop and some amplification. The physical properties of the quartz crystal inside the oscillator determines the resonant frequency.

 

[bobsmith1492]

I think they can actually just trim the quartz to the desired shape/size/whatever to adjust the frequency. It can be changed; you can get all kinds of different quartz oscillators. Google it!

Ok, I just did and learned some stuff. When you apply a voltage to a quartz crystal, it contracts; then, as it expands, it generates a pulse of electricity. So, by applying a voltage and using a couple of small capacitors (like you do when generating the clock for a microcontroller), you can cause it to act like an oscillator modeled by a 4th order (it looks like) RLC:C circuit. Check out this document: http://my.ece.ucsb.edu/yorklab/Useful%2...Tutorials/QuartzCrystalOscillators.pdf

 

[Calin]

There are quartz crystals for different frequencies: the ones in clocks are at a frequency that is a power of 2 in Hertz (like 65,536 Hz) so that you feed that frequency to a 16 bit counter and the result is a 1Hz signal (once a second). On ethernet cards the quartz crystal works (I know for sure only for 10Mbps cards) at 40MHz.
If you have an older discrete network card, look at it - there is a quartz (embedded into a shiny metalic case) that is marked in MHz