1. Combinational Circuit
Prof. Neeraj Bhargava
Kapil Chauhan
Department of Computer Science
School of Engineering & Systems Sciences
MDS University, Ajmer
2. Combinational circuit
Combinational circuit is a circuit in which we combine the different
gates in the circuit Means this is the combination of different logic
circuits.
Characteristics of combinational circuits are following −
The output of combinational circuit at any instant of time,
depends only on the levels present at input terminals.
The combinational circuit do not use any memory. The
previous state of input does not have any effect on the
present state of the circuit.
A combinational circuit can have an n number of inputs and
m number of outputs.
3. Types of Combinational circuit
Combinational Circuit are categorized into three
categories:
Arithmetic and Logical Function
Data Transmission
Code Convertor
5. Block diagram of Combinational
circuit
Combinational Circuit m outputs
n outputs
6. Adder
Adder is a combinational circuit.
It perform Arithmetic addition of inputs.
Adders are of Two Types :
1. Half Adder
2. Full Adder
7. Half Adder
This circuit is perform Addition of 2 bits and output produced by this
circuit is Sum(s) and Carry(c).
Block Diagram:
A Sum(s)
B Carry(c)
Half Adder
8. Half Adder
Truth table
Inputs Outputs
A B SUM(xor) CARRY(And)
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
9. This circuit is perform Addition of 3 binary bits and output produced
by this circuit is Sum(s) and Carry(c).
Sum is the additions of bits and Carry represent carry from previous
lower significant bits.
Block Diagram:
A Sum(s)
B Carry(c)
C
FULL ADDER
Full Adder
10. Full adder
Truth Table
Inputs Output
A B C SUM CARRY
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1