Transcript Introduction to Digital Electronics

Introduction
to Digital
Electronics:
The Integrated
Circuit
In digital devices, there re
only two values, usually
referred to as 0 and 1.
1
- there is a voltage
(usually 5 volts)
 0 – means there is no
voltage or 0 volts.
Integrated Circuits (IC)
an electrical lay-out etched on thin, small, layers of
semiconductor materials, incorporating or integrating
various components inside, with the result of having a
single device perform a particular function.
 The IC cannot be seen as it is completely covered by
the package, except in certain types of chips called
EPROMs, where there is a small circular opening or
window and what you will see is a very small
rectangular shaped shiny object- with very, very thin
wires around it, that is the integrated circuit.
-
ADVANTAGES OF INTEGRATED
CIRCUITS
1.
Integrated Circuits have low power
consumptions. Video cameras can survive on
small amounts of power because of their multifunction capabilities, miniature size and its
semiconductor properties. ICs operate even on
currents as low as a few milliamperes.
2.
Integrated circuits incorporate several functions and
circuitry in one small, thin rectangular-shaped object.
Using the theories of doping, it was possible to
incorporate diode as well as transistor circuits in a very
small area. Instead of using all of these components, you
just need a single IC and minimizing your worry about
design problems.

See how video cameras become smaller and smaller
nowadays? Or how computers become faster? This is
because some ICs manufactured nowadays have
incorporated functions of several older ICs. Imagine an old
computer as big as a large office room, being outperformed
by today’s powerful notebook size computers.
DISADVANTAGES OF
INTEGRATED CIRCUITS
1.
2.
When an IC is damaged, you cannot repair it.
You have to replace it. Since all the components are
integrated.
The sensitivity of the IC makes it important to
provide the proper packaging and storing for it.
The IC is also a device created under a clean
environment, having just enough impurities to
operate properly. Exposure to the outside world
might cause damage to the IC.
3.
ICs that are sensitive to static electricity can
easily be damaged by it.

We are one source of static electricity. Yes we can
destroy an IC by just holding it in the pins. Why
is this so? We carry static electricity, which had
been accumulated, for one thing, by rubbing with
other objects. So when you touch an IC pin, a
static electricity is discharged, transferring current
into the IC through the pins. An IC is a currentsensitive device and a large amount of current
passing through any of the pins might destroy the
chip.
FAMILIES OF INTEGRATED
CIRCUITS
1.
2.
3.
Number of components
Packaging
Purpose
Types of ICs According to the
Number of Components
 This
1.
2.
implies the number of miniaturized parts an
integrated circuit has.
SSI (Small Scale Integration) – For ICs with only
a few transistorized components , mostly less than
twenty.
MSI (Medium Scale Integration) – This group
includes ICs with 20 to a few hundred
transistorized components.
3.
4.
LSI (Large Scale Integration) – This involves
ICs which have components numbering in the
thousands. One LSI chip is equivalent to
several MSI components or several hundreds
or thousands of SSI components.
VLSI (Very Large Scale Integration) – This
comprises about 100,000 to as high as several
million miniaturized components in one chip.
This implies many functions that can be
performed by a VLSI chip.
Types of ICs According to
Packaging
1.
SIP (Single In-Line Package) – As the name
suggests, Single In-Line Package contain pins
aligned only one side, as seen in this type of
package can only accommodate a few pins,
since having to many pins using an SIP would
make the chip longer. This type only has a few
applications, an example of which is a resistor
pack.
2.
3.
4.
5.
DIP (Dual In-Line Package) – The pins are
arranged only on two sides of the package and
are arranged in a single line. Small ICs and the
first microprocessors are DIPs.
QIP (Quad In-Line Package) – The pins are
arranged on all four sides of the package, which
has a square shape.
PGA (Pin Grid Array) – This is similar to QIP but
it runs several layers deep.
TSOP (Thin-Small-Outline Package) – A special
quad package, but for smaller ICs like memory
components.
Types of ICs According to Function
1.
2.
3.
General Purpose Integrated Circuits – some
ICs were designed for ordinary use.
Hybrid Integrated Circuits – created by some
who would like to combine functions of
several general ICs and put them into a single
IC.
Application Specific Integrated Circuits –
this is more complex than the hybrid as the
entire purpose of the device will be placed in
one chip.
BASIC LOGIC GATES
 In
studying digital integrated circuits, one must start
with the simplest group of circuits, the SSIs. Since
these devices contain only a maximum of 10
transistorized components inside, these chips
normally contain a function used in boolean
algebra. Switching functions using boolean algebra
is the simplest operation used in digital circuits,
since it only involves a zero (0) and a one(1), much
like the false (if zero) and true (if one) signals of
boolean algebra.
THE NOT GATE

an inverter or NOT gate is a logic gate which
implements logical negation. The truth table is
shown
INPUT
OUTPUT
A
NOT A
0
1
1
0
In equation form Y=A
THE AND GATE
-
is a basic digital logic gate that implements logical
conjunction - it behaves according to the truth table.
This implies the statement if any among the list is false,
then the expression is false.
INPUT
Y=AB
OUTPUT
A
B
Q
0
0
0
0
1
0
1
0
0
1
1
1
THE OR GATE
-
This type of gate has two or more inputs, and if we
follow simple logic, this implies the statement if any
among the list is true, then the expression is true.
Y=A+B
Y
INPUT
OUTPUT
A
B
Y
0
0
0
0
1
1
1
0
1
1
1
1
THE NAND GATE
 This
type of gate has two or more inputs, and it does the
opposite of the And gate. That is why it is called NANDNegative AND.
Y
Y=AB
INPUT
OUTPUT
A
B
Y
0
0
1
0
1
1
1
0
1
1
1
0
THE NOR GATE
 This
type of gate has two or more inputs, and it
does the opposite of OR – Negative OR.
Y=A+B
Y
INPUT
OUTPUT
A
B
Y
0
0
1
0
1
0
1
0
0
1
1
0
THE XOR GATE
 This
type of gate has two or more inputs, and
it follows the exclusive OR Logic. This means if
the inputs are similar, the output is ‘0’. If the
inputs are not similar then the output is ‘1’.
 Y=A+ B where + is the
Y
symbol for XOR.
INPUT
OUTPUT
A
B
Y
0
0
0
0
1
1
1
0
1
1
1
0
PACKAGING LOGIC GATES
Most of today’s SSIs are cased in DIPs, or
dual-in-line packages. Each pin corresponds to a
number, with pin number 1 can be as found in the
drawing. This part of the IC is indicated by the half
crescent found on the IC, or by just looking at the
IC label, where pin no.1 is found on the lower left
as shown. The numbering of the pins are also
shown, following a U-shaped pattern.
Each boolean function in the IC corresponds
to a code number. Usually for TTL or TransistorTransistor Logic Integrated Circuits, the SSIs
have such code names as 7404s for inverters,
7408s for AND gates and 7432s for OR Gates
Single-input SSIs in Dual-InLine Packages
 The numbers 1
+Vcc A6 Y6 A5 Y5 A4 Y4
14 13 12 11 10 9 8
1 2
3
4
5
6
7
A1 Y1 A2 Y2 A3 Y3 Vss
to 14 are called
pin numbers
 Ai denotes
input of logic
gate i
 Yi denotes
output of logic
gate i
Example of Single-input SSI
+Vcc A6 Y6 A5 Y5 A4 Y4
A1 Y1 A2 Y2 A3 Y3 Vss
INPUT
OUTP
UT
A1
Y1
A2
Y2
A3
Y3
A4
Y4
A5
Y5
A6
Y6
Two-input SSIs in Dual-In-Line
Packages
 The
numbers 1
to 14 are called
pin numbers
 Ai denotes input
1 of logic gate I
 Bi denotes input
1 of logic gate i.
 Yi denotes
output of logic
gate i