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What's the minimum (physics first) to get an oscillator?
DiTBho:
this is as simple, as interesting :D
DiTBho:
@RoGeorge
I think a good answer comes from the Barkhausen Criterion. It says the principle of the oscillator is that when the feedback factor or the loop gain is one, then the overall gain of the oscillator circuit will be infinite.
So you have blocks, equations in both time and frequency domains, a lot of material, and a criterion!
IanB:
--- Quote from: RoGeorge on May 25, 2023, 11:15:56 am ---A spring+weight can oscillate, but it's not an oscillator because it's not constant amplitude.
--- End quote ---
What about the movement in a mechanical watch or clock? That contains a spring+weight oscillator that has constant amplitude.
External power input is a given for anything that is not a perpetual motion machine.
TimFox:
--- Quote from: IanB on May 25, 2023, 01:28:31 pm ---
--- Quote from: RoGeorge on May 25, 2023, 11:15:56 am ---A spring+weight can oscillate, but it's not an oscillator because it's not constant amplitude.
--- End quote ---
What about the movement in a mechanical watch or clock? That contains a spring+weight oscillator that has constant amplitude.
External power input is a given for anything that is not a perpetual motion machine.
--- End quote ---
This was supposed to start with physics.
In any freshman physics textbook, discussion of "simple harmonic oscillators" starts with the mass and spring, then we add an external force to get the "forced harmonic oscillator" to understand resonance phenomena, then we add damping to get the "forced damped harmonic oscillator" to understand the frequency response of such an oscillator with explicit energy loss during the oscillation.
The differential equations used in this development then appear in the analysis of analogous oscillators.
In engineering, we then look at "feedback oscillators", where the basic oscillator (e.g., RLC circuit) governs the timing of a packaged circuit to generate a continuous oscillation from an external power source.
jwet:
Barkhausen doesn't cover relaxation oscillators. Make an RC cicuit, connect it to a 100v source, the C will charge up, now, put a neon bulb across the cap, it will trigger at 70v discharging the cap and keep going. You could make a strained argument that the neon lamp has negative resistance which is gain etc, but this isn't how it operates really.
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