special semiconductors

Construction of Uni Junction Transistor (UJT)

This entry is part 2 of 4 in the series Special Semiconductors

This transistor is similar to the BJT except it has only one junction. The schematic view of the UJT is given below –

Construction of Uni Junction Transistor (UJT)

As shown in above figure, the UJT is made up of an n-channel with a p-layer inserted into the channel nearer to base-2 than base-1.

Thus it has one PN junction with two internal resistances Rb1 and Rb2 such that Rb1 is the internal resistance between base-1 and emitter. And Rb2 is the internal resistance between base-2 and emitter. So it is clear that Rb1 >> Rb2 because emitter layer is nearer to base-2 than base-1.

The important parameter of the UJT is known as intrinsic standoff ratio as follows –

η = Rb1 / ( Rb1 + Rb2 )

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Dattaraj Vidyasagar
Dattaraj Vidyasagar

Author on this website. He is veteran of Core Electronics since last 36+ years. ATL Mentor of Change, Niti Ayog, Govt. of India, Google Certified Educator, International Robotics Trainer and author of 18 books on electronics, robotics, programming languages and web designing... ➤➤

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