3. INTRODUCTION
Digital
Concerned with the interconnection among digital components and
modules
Best Digital System example is General Purpose
Computer
Logic Design
Deals with the basic concepts and tools used to design digital
hardware consisting of logic circuits
Circuits to perform arithmetic operations (+, -, x, ÷)
DMISEU-IVDL
4. Digital Signal : Decimal values are difficult to represent in
electrical systems. It is easier to use two voltage values.
Digital Signals have two basic states:
1 (logic “high”, or H, or “ON”)
0 (logic “low”, or L, or “OFF”)
Digital values are in a binary format. Binary means 2 states.
A good example of binary is a light (only ON or OFF)
DMISEU-IVDL
7. Logic Gates
A logic gate is an electronic circuit which makes
logical decisions.
Types of Gates
OR Gate
AND Gate
Not Gate
NAND Gate
NOR Gate
EX-OR Gate
EX-NOR Gate
DMISEU-IVDL
8. DMISEU-IVDL
OR Gate
• The OR gate performs Logic addition, it
is known as OR function.
• The OR gate has two or more inputs
and only one output.
Y = A+B
8
10. AND Gate
The AND gate performs Logic addition, it is
known as AND function.
The AND gate has two or more inputs and only
one output.
Y = A.B
DMISEU-IVDL
12. NOT Gate
• The NOT gate performs the basic logical function called
inversion or complementation.
• The purpose of the gate is to convert one logic level into
the opposite logic level.
DMISEU-IVDL
13. NOT Gate Symbol and Truth Table
DMISEU-IVDL
Input
A
Output
F = A
0 1
1 0
14. NAND Gate
• NAND is a contraction of the NOT-AND gates.
• It has two or more inputs and only one
output.
DMISEU-IVDL
18. Ex-OR Gate
• An Exclusive-OR gate is a gate with two or more inputs
and one output.
DMISEU-IVDL
Input Output
F=
A B
0 0 0
0 1 1
1 0 1
1 1 0
19. DMISEU-IVDL
Ex-NOR Gate
• An Exclusive-NOR gate is a gate with
two or more inputs and one output.
DMISEU-IVDL
Input Output
F=
A B
0 0 1
0 1 0
1 0 0
1 1 1
29. Combinational Circuits
DMISEU-IVDL
Combinational logic circuits are circuits in which
the output at any time depends upon the combination of
the present input signals.
• Adders
• Multiplexers
• De-Multiplexers
• Decoders
• Encoders
