ujt

1. UJT
Unijunction Transistor(UJT)

2. UJT
•UJT is a three-terminal semiconductor
diode.
•Three terminals; Emitter, Base 1 and Base 2.
•It has only one PN Junction

3. Construction &
Symbol:

4. UJT
• UJT consists of a lightly doped N-type Si bar into which heavily doped
P-type material is diffused.
• P-type material is closer to the B2.
• In the symbol the arrow at the junction represents that the flow of
conventional current from the emitter to B1.

5. Equivalent Circuit of UJT:

6. • Diode ‘D” represents PN Junction.
• Interbase resistance between B2 and B1 is RBB.
• RBB = RB1 + RB2
• RB1 > RB2
RB1 is represented as variable resistor as its resistance various with the
variation of the biasing voltage.