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Homework Help: Trying to explain how a Relaxation Oscillator UJT circuit works

  1. May 26, 2012 #1


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    http://img689.imageshack.us/img689/7084/ujte.jpg [Broken]

    This is a Relaxation Oscillator circuit with UJT. I need to A) Explain what is UJT, explain its relation ratio of η for the UJT, and explain what Vp is. And in B) Explain how does the circuit work, and what is the output (or turnout) of the circuit

    Trying to use my own words

    UJT is a uni-junction transistor that has a single emitter and two bases. As long as the voltage in the emitter is smaller than the breakthrough voltage (Vp) , the UJT acts as disconnection.
    When the voltage in the emitter gets to the same voltage as Vp, the resistance at the base is broken through B1, and when the voltage in the emitter drops to a minimal value Uv, UJT is back to cutoff.

    relation coeffcient - η = Rb1/(Rb1+Rb2)

    Vp is "peak voltage" or "breakout" voltage. When the voltage in the emitter arrives to Vp then the UJT opens up (broken though).

    (Hope I didn't lose anyone by now!)

    B) This circuit generates pulses. Its made out of UJT and a capacitor. The capacitor is loaded from the source and when it reaches Vp, the UJT opens up and current flows from the Emitter through B1.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. May 26, 2012 #2

    I like Serena

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    Well, I haven't learned about UJT's before, but after googling it I'm drawing the conclusion that you summed it up nicely. :)
    Actually, I like your explanation better than some others on the internet.

    I'm turning into an electronics expert thanks to you!
  4. May 31, 2012 #3


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    Much appreciated :)
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