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thebugger
modified 9 years ago

Atypical VHF Oscillator

5
4
238
05:11:14
Shake to start The emitter follower with the voltage gain, seems a good start to a VHF oscillator. Since there is virtually no Miller Effect, the gain shouldn't be restricted to low frequencies, but should extend up to the VHF/UHF spectrum. The thing you need is voltage gain and feedback. Normally an emitter follower doesn't have voltage gain, but with the modified version, it should get oscillating. This is something you won't be able to breadboard, though. At these frequencies, special layout measures are usually taken, to minimize stray capacitance/inductance disturbance. Something interesting I noticed, the frequency doesn't seem to drift, even while the wave is rising, which is somewhat atypical. Most VHF oscillators are quite unstable.
published 9 years ago
hurz
9 years ago
This circuit is easy to analyse http://everycircuit.com/circuit/5872363111710720
jpoulin0901
9 years ago
Wow, the current in the tank rises to around 100mA in the sim. I even tried adding series resistance to each of the inductors such that their Q is finite and the circuit still performed just as well. Is there a reason you omit the series resistance in small inductors? I get that the resistance is tiny but so much realistic analysis is impossible when you're left to divide by zero all over the place. Anyway, have you ever calculated the output power from this bad boy? Seems like it could make a good RF beacon for finding your keys or something.😎
zorgrian
9 years ago
Why do you say this is a 'typical' vhf oscillator?
zorgrian
9 years ago
Or do you mean atypical?

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