dohzer
Member level 1
Crystal Clock Source - Tuning for Low Voltage
So I've constructed the circuit shown in Fig. 8 from this Linear Technology Clock Source App Note on a bit of Veroboard, but I don't want to run it at 24V.
Now... when I say "Fig. 8", at the moment I don't want variable frequency, so I've replaced the varactor diode with a fixed capacitor, and omitted the variable capacitor and 100kΩ resistor.
I was a little lost with the "tuning process", but I managed to keep it oscillating all the way down to the desired 3V supply by connecting four trim-pots in-place of the 10kΩ, 2k7Ω, 12kΩ and 4k7Ω resistors and adjusting one at a time, purely trial and error.
The default circuit would only oscillate down to about 12Vdc.
In order to adjust for the supply, what are the goals that will keep it oscillating?
Not overloading the crystal? Keeping the transistor biased in the linear region?
Are there some simple rules to follow for calculating the values rather than simply trialling them?
So I've constructed the circuit shown in Fig. 8 from this Linear Technology Clock Source App Note on a bit of Veroboard, but I don't want to run it at 24V.
Now... when I say "Fig. 8", at the moment I don't want variable frequency, so I've replaced the varactor diode with a fixed capacitor, and omitted the variable capacitor and 100kΩ resistor.
I was a little lost with the "tuning process", but I managed to keep it oscillating all the way down to the desired 3V supply by connecting four trim-pots in-place of the 10kΩ, 2k7Ω, 12kΩ and 4k7Ω resistors and adjusting one at a time, purely trial and error.
The default circuit would only oscillate down to about 12Vdc.
In order to adjust for the supply, what are the goals that will keep it oscillating?
Not overloading the crystal? Keeping the transistor biased in the linear region?
Are there some simple rules to follow for calculating the values rather than simply trialling them?
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