electronics. UJT

1. SUBJECT : ELECTRONICS
TOPIC : UJT
PRESENTED BY :-

2. CONTENT
 WHAT IS UJT
 CONSTRUCTION
 WORKING
 V- I CHARACTERISTICS

3. What is UJT ?
 Unijunction Transistor is a semiconductor switching device having 2
layers and 3 terminals
 It is called so because of the presence of only one junction.
 It has the ability to limit large power with a small input signal and is also
known as a double base diode.

4. Construction of UJT :-
 In Unijunction Transistor, the PN Junction is formed by lightly
doped N type silicon bar with heavily doped P type material on
one side.
 The ohmic contact on either ends of the silicon bar is termed as
Base 1 (B1) and Base 2 (B2) and P-type terminal is named as
emitter.

5. Working of UJT :-
 The N-type channel consists of two resistors RB1 and RB2 in
series
 And a equivalent diode D representing the PN junction
 The emitter PN junction is fixed along the ohmic channel
during its manufacturing process

6. Working of UJT :-
 The variable resistance RB1, is connected between the terminals
Emitter (E) and Base1 (B1) , the RB2 between the Emitter(E) and
Base2 (B2)
 Since the PN junction is more close to B2 , the value of RB2 will
be less than the variable resistance RB1

7. Working of UJT :-
 The voltage across resistance RB1 of the voltage divider circuit
is calculated by
𝑉𝑅𝐵1 =
𝑅𝐵1
𝑅𝐵1 + 𝑅𝐵2
+ 𝑉𝐵𝐵

8. V – I Characteristics of UJT :-

9. Reference :-
 https://electricalfundablog.com/unijunction-transistor-ujt-
construction-working-characteristics-curve-applications
 https://electricalfundablog.com/unijunction-transistor-ujt-
construction-working-characteristics-curve-applications/