The document discusses the history and development of the transistor from the vacuum tube, describing how the transistor revolutionized electronics by being smaller, more efficient, and reliable than vacuum tubes. It explains the basic structure and functioning of different types of transistors like BJT, MOSFET, and JFET transistors. The document also covers transistor applications in modern electronic devices and circuits.

2. Seminar
Amaljo Joju E
EEE

5. Transistor is known as
WONDER BABY IN
ELECTRONICS
It is the fundamental
bulding blocks of modern
electronic devices

6. Transistor
is a 3
terminal
device
It is
represented
by →→

7.  Before transistors were
invented, circuits used
VACUUM TUBES:
Fragile, large in size, heavy,
generate large quantities of
heat, require a large amount of
power

8.  John Ambrose
Fleming -developed
the Vacuum Tube
 a device that modify a signal by
controlling the movement of
electrons in an evacuated space.
 The electrons flow only from
filament to plate creating a diode
(a device that can conduct current
only in one direction)

9. Aug 20 2007 9

10. 1947 The first integrated
transistor (Bell Telephone
Laboratories)
Bardeen and Brattain built
the point contact transistor.
They made it from strips of gold
foil on a plastic triangle, pushed
down into contact with slab of
germanium

11.  Shockley make the
Junction transistor
(sandwich).
 This transistor was
more practical and
easier to fabricate.
 The Junction Transistor
became the central
device of the electronic
age
http://www.ecse.rpi.edu/Homepages/schubert/Unused%20stuff/Educational%20resources/
Picture%20First%20junction%20transistor.jpg

14. • Doping: adding small amounts of other
elements to create additional protons or
electrons
• P-Type: dopants lack a fourth valence electron
(Boron, Aluminum)
• N-Type: dopants have an additional (5th)
valence electron (Phosphorus, Arsenic)
• Importance: Current only flows from P to N

15. • Diode: simple P-N
junction.
• Forward Bias: allows
current to flow from P to N.
• Reverse Bias: no current
allowed to flow from N to
P.
• Breakdown Voltage:
sufficient N to P voltage of
a Zener Diode will allow for
current to flow in this
direction.

16. MOS - Metal Oxide
Semiconductor
FET - Field Effect
Transistor
BJT - Bipolar Junction
Transistor
◄

18. There are two types of
BJTs, the npn and pnp
The two junctions are
termed the base-emitter
junction and the base-collector
junction
The term bipolar refers to
the use of both holes and
electrons as charge carriers
in the transistor structure
In order for the transistor to
operate properly, the two
junctions must have the
correct dc bias voltages

20. • High potential at
collector
• Low potential at
emitter
• Allows current flow
when the base is given
a high potential

22. BJT npn Transistor
 1 thin layer of p-type, sandwiched between 2 layers of n-type.
 N-type of emitter: more heavily doped than collector.
 With VC>VB>VE:
 Base-Emitter junction forward biased, Base-Collector reverse
biased.
 Electrons diffuse from Emitter to Base (from n to p).
 There’s a depletion layer on the Base-Collector junction no flow
of e- allowed.
 BUT the Base is thin and Emitter region is n+ (heavily doped) 
electrons have enough momentum to cross the Base into the
Collector.
 The small base current IB controls a large current IC

23. • The metal-oxide semiconductor field-effect
transistor (MOSFET) : the gate is insulated
from the channel by a silicon dioxide (SiO2)
layer

24.  Three Types of Field Effect Transistors
 MOSFET (metal-oxide-semiconductor field-
effect transistors)
 JFET (Junction Field-effect transistors)
 MESFET (metal-semiconductor field-effect
transistors)

26.  TempFET – MOSFET’s with temperature
sensor
 High Electron Mobility Transistors (HEMTs) –
allows high gain at very high frequencies
 Darlington – two transistors within the same
device, gain is the product of the two
inidvidual transistors

27.  Four-layer PNPN semiconductor devices
 Behaves as two transistors in series
 Once on, tends to stay on
 Once off, tends to stay off

28.  Triode alternating current switch
 Essentially a bidirectional thyristor
 Used in AC applications
 Con: Requires high current to turn
on
 Example uses: Modern dimmer
switch

29. Switching Amplification
Variable
Resistor