Chapter 1:
Bipolar Junction Transistor (BJT)
Assoc. Prof. Pham Nguyen Thanh Loan
September, 2024
Contents
Structure and operation of BJT
Different configurations of BJT
Characteristic curves
DC biasing method and analysis
🞑 Base bias
🞑 Collector-feedback bias
🞑 Voltage divider bias
AC signal analysis
Impact of other parameters (temperature, leakage
currents)
2
The content of these slides are based on the book titled “Electronics Devices and Circuit theory of
Robert Boylestad”
Structure and operation of BJT
❖BJT structure
BJT :Bipolar Junction Transistor
2 kinds of BJT: NPN & PNP
3 terminals: E, B và C
E: Emitter; B: Base, C: Collector
Base located in the middle:
thinner than E & C; and lower
dope
3
So:IE = IC + IB
❖Bias condition for 2 junctions: JBE & JBC
Junction BE in forward bias: electrons
(e) move from E region to B region to
create the current IE (diffusion current;
flow of majority carriers)
Junction BC in reverse bias: e that
moved from E to B then move from B to
C to create the current IC (drift current,
flow of minority carriers)
The combination of some electrons with
holes in B region creates the current IB
4Structure and operation of BJT
3 terminals: B, E và C
Arrow instructs the current
direction between B & E
Conventional current is the
flow of positive charges
(holes)
NPN: B → E
PNP: E → B
❖BJT symbol
IB
IC
IE
5Structure and operation of BJT
❖Explain the symbol of BJT?