Thanks for all the replies.
My project is basically a heterodyne audio oscillator : The crystal oscillator circuit I'm asking about here will be used as the main reference frequency and will feed a divider circuit.
I read (somewhere) that oscillators based on a CMOS inverter (Pierce?) are not that good... also that you shouldn't use Schmitt type inverters as they basically have too much gain. I don't
really want to have an extra IC (e.g. 74HCU04) just to use one out of the six inverters in it : So my thoughts turned to a simple Colpitts circuit based around a discrete transistor. This would feed a spare Schmitt inverter (74HC14) that I'm using before going to the divider.
I've seen some circuits that advocate using high-value bias resistors so as not to 'load' the crystal and ruin it's Q, I've also seen other circuits where the bias resistors were less than 10k !
There's never any mention of 'drive' levels.
Does this help to explain things ?
Of course, maybe I'm over thinking any perceived problems.
I have not had any success with crystal oscillators in circuit simulators either.
Quote:
Originally Posted by Jon_G4MDC
The main benefit of LT Spice is the virtual probe which can tell you Voltage across the crystal and then with ESR value you know the dissipation.
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- thanks for that info, makes a lot of sense !
David (Radio Wrangler), I'll try and read up more about the subject in the references you've given.
Andy