I'm moving my oscillator from the CD drive to my DAC board. Signals go via I2S. This works really well, but the question is: what oscillator circuit should I build? Should I pick the easy way, buying a simple canned oscillator, hook up a crystal and a chip that pulls it all the way from 10kHz to 10MHz, or go all out with a Colpitts (or friends) that I build from discrete transistors. As always, low jitter is the ultimate goal.
Greetings,
Børge
Greetings,
Børge
there are so many high speed comparators out there that it seems pointless to build it from scratch -- check out Analog Devices website.
A sinusoidal crystal oscillator will have lower jitter because it doesn't overdrive the crystal, so a Colpitts would be fine.You want to maximise the Q of the resonant circuit, so the crystal should ideally see a low impedance at each end. The oscillator needs to be buffered before feeding the comparator. If you don't include a good buffer, the sudden changes in input impedance of the comparator as it switches will upset the oscillator. Current feedback video op-amps such as EL2030 and derivatives are useful here.
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