crystal oscillator

You're going at it backwards.

You pick a type of oscillator to match what you want to do.

So if it's an overtone crystal, you make sure you use an oscillator that will have it oscillating in the overtone mode.

It might help, besides asking in sci.electronics.basics where this question likely really belongs, is to ponder what an overtone is, and what you are trying to do when getting a crystal to oscillate in overtone mode.

Understand that, and you'll have a better idea of what you are seeking.

Michael

Google do.

I would not call crystal oscillator design basic...

Especially not at 100MHz, which is likely to be a 5th overtone design.

James Arthur

You don't even need to go 3rd harmonic to get 100MHz. You can get fundamental 100MHz crystals.

You can get 100MHz with a transistor like the 2N2222, making a fairly simple oscillator. The transistor doesn't have enough gain to take off at the 3rd.

yes

If you have installed LTspice SwitcherCadIII look in this directory, "C:\\Program Files\\LTC\\SwCADIII\\examples\\Educational"

There's a few example designs of colpitts and clapp oscillators.

If you never heard of this free software get it here;

Those inverted mesa (I-M) crystals are cool, but for that kind of money why not buy Prince Albert in a can?

Of course it all depends on our guerilla (hit-and-run) poster's needs: stability, quantity, power, accuracy, cost, designer's time, etc. For now, 100MHz AT overtone crystals have ~5-10x higher Qs, age better and cost less.

OTOH, a 3rd overtone I-M looks pretty slick at 300MHz, and they look really interesting as filters.

Thanks for the reminder -- last time I considered I-M they were boutique, exotic parts. I just read that they're down to only 3x the price, which isn't really all that bad. Best, James Arthur

oscillator for

at

Due to certain reason, I had to used the 3rd crystal. And I need this oscillator circuit to drive my IC which had a build in transistor inside.

right now, I can't make the circuit work...so need some help on the calculation for the capacitance and inductance.

oscillator for

at

Due to certain reason, I had to used the 3rd crystal. And I need this oscillator circuit to drive my IC which had a build in transistor inside.

right now, I can't make the circuit work...so need some help on the calculation for the capacitance and inductance.

Only because the OP said he wanted to make a crystal oscillator.

The GreenRay OCXO is a lot better, if cost is no object.

I think that will be true basically forever. The Q of an overtone will always come out higher. You do have to be very careful in your frequency selector section to make sure that it doesn't end up adding a bunch of close in noise to take advantage of this though.

In article , max wrote: [.... 100MHz ...]

I assume that the L and C in question are in the frequency selector network.

The first step is to ignore the issue and replace the LC circuit with a magic resistor. This magic resistor has no resistance at DC and some fixed value at high frequencies.

You may need to place a real capacitor or inductor in series or parallel with this magic resistor to make the oscillator design workable.

Now, you work out what resistance the magic resistor must have for proper operation.

Now the problem is one of making an LC circuit with the needed resistance at resonance and the right resonant frequency. Generally, you want to go for a low Q tuned circuit. If this is AT cut, the Q can be quite low. Lets say 3. With SC cut crystals the Q needs to be higher. Lets say 20.

The exact Q you want is enough to ensure that every crystal the meets spec must run on the desired frequency but not much more. A higher Q tuned circuit will have a rapid phase vs frequency slope. This will allow it to start causing drift.