UJT Interview Question Answer

Important Question of UJT

In this post, some of the important questions of UJT are given. It includes full form of UJT, terminals of UJT, inter-base resistance, intrinsic stand-off ratio and application of UJT.

Construction of UJT

State the full form of UJT.

  • Unijunction transistor

Which are the three main terminals of the UJT?

UJT terminals

  • Base 1, Base 2 and Emitter

How many PN junction diode the UJT consists of?

  • One

Whether two base terminals are interchangeable in the UJT?

  • Yes

What do you mean by inter base resistance?

Inter base resistance

  • The resistance between two terminal base 1 and base 2 is called as inter base resistance. 
  • It is resistance of the N type material.

Explain the term : Intrinsic stand-off ratio

Intrinsic stand-off ratio

  • It is defined as the ratio of resistance between base 1 to emitter (RB1) to the inter base resistance RBB
  • Its symbol is eta ( η ).     
                                              η = RB1 / RBB

UJT: Valley Point and Peak Point

State the operating region of the UJT.

  • The UJT operates in the peak point to the valley point region.

Define : Valley current

Valley current

  • The valley current is similar to holding current in the SCR. 
  • It is minimum current requires to keep the UJT in on condition. 
  • The UJT turns off when the emitter current reduces below valley current.

Define : Peak voltage in the UJT

Peak voltage

  • It is an emitter voltage at which the UJT operates or turn on.

        VP = ηVBB + VD

        VP =  Peak point voltage

        VBB  = Voltage between base 1 and emitter

        VD = Voltage across diode and

        η =  Intrinsic stand-off ratio

Which types of pulses are generated in the UJT relaxation oscillator circuit at terminal B1 and B2?

  • Positive train of pulses at terminal B1 whereas negative pulses at terminal B2

Which parameters greatly affect the oscillator frequency in the UJT relaxation oscillator?

UJT relaxation oscillator

  • The oscillator frequency in the UJT relaxation oscillator depends upon the RC time constant circuit. 
  • The time period of the relaxation oscillator is given by T = RC loge [ 1 / ( 1 – η )] ( Where η = Intrinsic stand off ratio )

Applications of UJT

State the application of the UJT.

Application of UJT

  • Timing circuits
  • Relaxation oscillators
  • Trigger circuits
  • Non-sinusoidal oscillators
  • Saw tooth generators
  • Timing circuits

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