Lecture 1: Introduction to
Bipolar Junction Transistor (BJT)
, The Invention
The First Transistor: On Dec 23, 1947, three scientists led by Dr. William Shockley at
the Bell Telephone Laboratories demonstrated the amplifying action of the first transistor .
(Courtesy Bell Telephone Laboratories.)
Co-inventors:
Dr. William Shockley
(seated);
Dr. John Bardeen (left);
Dr. Walter H. Brattain.
Honored with
Nobel Prize in
Physics in 1956
Important Features (compared to Vacuum tubes):
- three terminal solid-state device - requires less power
- smaller and lightweight - lower operating voltage
- has rugged construction - more efficient
- no heater requirement
2
, The Structure
The Bipolar Junction Transistor (BJT)
Bipolar: both electrons and holes are involved in current flow.
Junction: has two p-n junctions.
Transistor: Transfer + Resistor.
It can be either n-p-n type or p-n-p type.
Has three regions with three terminals labeled as
i. Emitter (E)
ii. Base (B) and
iii. Collector (C) 3
, The Structure: npn & pnp
Base is made much narrow.
Emitter is heavily doped (p+, n+).
Base is lightly doped (p-, n-).
Collector is lightly doped (p, n).
4
Bipolar Junction Transistor (BJT)
, The Invention
The First Transistor: On Dec 23, 1947, three scientists led by Dr. William Shockley at
the Bell Telephone Laboratories demonstrated the amplifying action of the first transistor .
(Courtesy Bell Telephone Laboratories.)
Co-inventors:
Dr. William Shockley
(seated);
Dr. John Bardeen (left);
Dr. Walter H. Brattain.
Honored with
Nobel Prize in
Physics in 1956
Important Features (compared to Vacuum tubes):
- three terminal solid-state device - requires less power
- smaller and lightweight - lower operating voltage
- has rugged construction - more efficient
- no heater requirement
2
, The Structure
The Bipolar Junction Transistor (BJT)
Bipolar: both electrons and holes are involved in current flow.
Junction: has two p-n junctions.
Transistor: Transfer + Resistor.
It can be either n-p-n type or p-n-p type.
Has three regions with three terminals labeled as
i. Emitter (E)
ii. Base (B) and
iii. Collector (C) 3
, The Structure: npn & pnp
Base is made much narrow.
Emitter is heavily doped (p+, n+).
Base is lightly doped (p-, n-).
Collector is lightly doped (p, n).
4
