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 (R_B1) to the inter base resistance R_BB. 
• Its symbol is eta ( η ).     

                                              η = R_B1 / R_BB

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.

        V_P = ηV_BB + V_D

        V_P =  Peak point voltage

        V_BB  = Voltage between base 1 and emitter

        V_D = 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 log_e [ 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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