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simple one transistor oscillator


Full Member level 2
Dec 18, 2013
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I saw a YouTube video that showed a circuit with one transistor that oscillates. unfortunately, I do not access to it.
I plotted schematic of the circuit in ltspice( attached file) as was in that video.
  1. where does the base of the transistor connect?
  2. Is the position of emitter and collector true or it must be reversed?
  3. how can I change the circuit to oscillate between 5 and 8 volts, namely these two values are the minimum and maximum amplitude of oscillation.
any guidance is appreciated.

The shown circuit connects the transistor and does surely not oscillate. It's unclear which type of oscillator you are looking for.

At first sight I'm not aware of a single RC/single transistor oscillator topology. Single transistor phase shift oscillator with threefold RC feedback is an option. Or a relaxation oscillator with two transistor or a four-layer transistor, e.g. UJT.
I don't think it demonstrates negative resistance as claimed, at least not in a usable form. I think it work by avalanche breakdown of the transistor junction. In post #1 the schematic certainly will not work, all it does is drop the supply to about 1.2V across the diode and transistor. The collector and emitter have to be swapped for it to work.

A similar circuit is widely used in lamp failure circuits but uses a diac instead of a transistor:
voltage -- resistor --- diac to 0V
with a capacitor across the diac.

Interestingly, the link in:
where it shows the two transistor version does work and replacing one or both transistors with JFETs makes it even better. I have successfully made a regenerative radio receiver using JFETS that way and varying the supply voltage to optimize the negative resistance performance.

O.k., according to the link, BE avalanche breakdown can work, so the post #1 circuit isn't completely off-topic. However, without a current limiting resistor, the transistor will be probably die fast.

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