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Doctors Medicines MCQs Q&A

  1. Resistive triggering circuit
  2. Resistance-capacitance triggering circuit
  3. Diac-Triac circuit
  4. UJT based relaxation oscillator circuit
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1 Answers

Option 4 : UJT based relaxation oscillator circuit

UJT relaxation oscillation:

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  • The uni-junction transistor (UJT) has two doped regions with three external leads. It has one emitter and two bases.
  • The emitter is heavily doped having many holes.
  • The UJT is used to trigger the SCR. 
  • The trigger voltage is equal to the capacitor voltage since the capacitor is connected between the anode and the ground.
  • When the capacitor charges to the trigger voltage, UJT turns ON, discharging the capacitor through R4, thus turning ON the SCR.
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