Nexxen wrote on 2026-10-28, 23:44:
wierd_w wrote on 2026-10-28, 20:28:
The trimming cap is the expensive bit.
Otherwise its approx 100nH inductor + 247pF ceramic cap, for ~32mhz.
What would I need beside the above to create this?
some transistors, and or an opamp chip.
The theory and principle can be found here:
https://www.eleccircuit.com/simple-transistor … tts-oscillator/
The basic components of the lc resonator (the inductor and the cap), will "bounce" a stored charge on the capacitor, converting it back and forth between charge and EM field in the inductor, at a frequency paired with the values of these components. Because these have resistance, the signal quickly dies out.
However, you can use a set of suitable transistors and an op-amp to supply more input voltage, and collect the sinusoid output of the tank so that it does not die out. Some example circuits are provided in the link. Just substitute suitable components for your 32mhz signal, where appropriate.
Logic level devices will want square waves, not sinusoids though. So, using 1 more transistor on the output sinusoid across the gate, with a voltage source, will turn it into a square wave. (the peaks of the sinusoid are rectified, then fed to the gate of a transistor. When the peak is present, the transistor conducts. When it is not, it does not. This will give you an amplified square wave, derived from the tuned sinusoid. The transistor needs to have a switching frequency greater than the desired output frequency.)
You can create a circuit that you can manually adjust the output signal from this way, from some discrete parts.
It will draw more power though. The idea here is to find out what the frequencies you actually need are, and then get a suitable crystal, not to substitute the part. (but, I suppose if you dont care about it being bulky, ugly, and power hungry, you could.)
More or less, "Here is a way to make a tunable clock source, for diagnostic purposes."
