Transcript Chapter 4

Chapter Four
Active Components &
Integrated Circuits
Introduction
Basic solid-state electronic devices
are described, and some idea of the
powerful uses of digital electronics is
given.
Active Electrical Components
Background
 Passive
vs.
Active
electrical
components.
 Active: require an external source of
power in order to work.
 Vacuum Tubes are an example of the
early types of active components.
 Many electronic functions were possible
using tubes, but there were serious
limitations, these are:
Vacuum tubes
 Tubes require high voltages to operate (250
– 300V).
 They dissipate large amounts of heat.
 They wear themselves out and need to be
periodically replaced.
 They were expensive to produce and
fragile.
 Tubes still find their way in certain
applications (microtubes in the military).
Transistors
These replaced vacuum tubes in many
applications, because:
 They are small in size.
 They require little power to operate.
 They are mechanically very rugged.
 They are operated on low voltages
(12V or less).
They
are
extremely
simple
in
structure.
What is a transistor?
 A piece of semiconductor material chemically
treated to have some desired electrical
properties.
 Semiconducting materials conduct electricity
better than insulators but much poorer than
conductors.
 Typically it has three terminals (BJT: Emitter,
Base, Collector; MOS: Drain, Gate, Source).
 Current amplifier: allows small (base) current to
control much larger current (collector).
What is a transistor?
 Can be used as ON/OFF Switch (Electronic
switch)
 In order to operate the transistor it should be
connected in a circuit with the proper
components
Bipolar junction transistor
MOS transistor
Integrated Circuits
 Transistors
and
their
associated
circuits
are
manufactured on the same piece of semiconductor
material (chip or IC)
 Microprocessors contain millions of transistors are
fabricated on a single chip due to the development in IC
technology.
 ICs are used in both digital and analog applications,
there are thousands of different chips in the market.
 The operating parameters & schematic diagrams are
provided in Data books put out by the manufacturing
companies (TTL, Synertek, Intel, Motorola).
Digital Electronics
Electronics can be divided into two areas:
 Digital: based on the binary number
system and the output can assume only
two values (ON=1=+5V DC, OFF=0=0V
DC).
 Analog (amplifier output might be any
voltage from say -5V to +5V).
 Digital electronics is the basis of
operation of computers.
The Binary Number System
 Numbers are represented in computers
using the binary number system.
 The reason for using the binary system is
that the transistors internal to the
computer chip act as simple switches.
 The decimal system can be converted to
the binary system so the binary system
does not limit the capability of a computer
to make calculations.
Logic Families
 Families differ in: the way the transistors
are connected together, switching speeds,
power consumption, operating voltage
levels, and other electrical characteristics.
 TTL: Transistor-Transistor Logic
 CMOS:
Complementary
Metal
Oxide
Semiconductor
 ECL: Emitter Coupled Logic
 Applications determine which family to
use.
Simple logic functions
Inverter.
 Symbol
A
B
 Truth table
A
B
0
1
1
0
Simple logic functions
AND Gate
 Symbol
 Truth table
A
0
0
1
1
B
0
1
0
1
C
0
0
0
1
Simple logic functions
 OR Gate
 Symbol
 Truth table
A
0
0
1
1
B
0
1
0
1
C
0
1
1
1
Example
15 cents toll.
Only nickels (5 cents) and dimes (10 cents) can be
deposited.
N= number of nickels deposited
D= number of dimes deposited
G= command to raise gate
0 N 3
0  D 1
G=0 if 15 cents is not deposited
G=1 if 15 cents is deposited
Circuit Implementation
G=n1n2+n1d1, n1=1Nickel, n2=2Nickels,d=1 Dime
The truth table
n1
0
0
0
0
1
1
1
1
n2
0
0
1
1
0
0
1
1
d1
0
1
0
1
0
1
0
1
g
0
0
0
1
0
1
1
1