EMRFD Message Archive 8283
Message Date From Subject 8283 2013-02-22 16:13:28 Glen Leinweber A no-bias LC oscillator Have been looking at the ubiquitous Pierce crystal oscillators used to
very many digital circuits. Perhaps the 74HCU04 logic gate can be used in
an LC-type VFO, with reasonable performance? Yes!
Turns out that an LC version, optimized to match the amplifier Z to the
resonator Z looks very much like a Vackar oscillator. Changing the input's
capacitive voltage divider to a tap on the resonator's inductor results in
an oscillator with only reactive components (one coil, two capacitors).
Have documented measurements and design here:
8287 2013-02-23 03:44:13 Ashhar Farhan Re: A no-bias LC oscillator There is also the franklin variation where a parallel tuned circuit is
lightly coupled to the input and output of a cascade of two inverting gates
(each biased to linear region with a feedback resistor). I have tried it
recently and it works quite well too. I am not sure of the phase noise
though. I only have a bitx to hear the phase noise with. the stability was
amazingly good with 2.2pf coupling capacitors (using 0805 smd capacitors).
i would also make sense to evaluate a 'tickler' circuit where a secondary
drives the feedback, back into the tank. i haven't evaluated this
i seem to get much lesser temperature drift with smd components than the
leaded components. any explanations?
8289 2013-02-23 13:58:26 Dana Myers Re: A no-bias LC oscillator