ripple adder
Post on 16-Jul-2015
295 Views
Preview:
TRANSCRIPT
ByT.Mounika
Introduction Arithmetic operations like addition, subtraction,
multiplication, division are basic operations to be
implemented in digital computers using basic gates like
AND, OR, NOR, NAND etc.
Among all the arithmetic operations if we can implement
addition then it is easy to perform multiplication (by
repeated addition), subtraction (by negating one operand)
or division (repeated subtraction).
Binary addition is a fundamental operation in most digital
circuits
There are a variety of adders, each has certain
performance.
Each type of adder is selected depending on where the
adder is to be used.
Ripple carry adder is suitable for small bit applications
Basic adder circuit
A combinational circuit that adds two bits is called a half adder
A full adder is one that adds three bits
Full Adder
sum
carry3 inputs
Truth Table of fulladder
Input
A
Input
B
Input
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
Ripple carry adderThe ripple carry adder is constructed by cascading full
adder blocks in series
The carryout of one stage is fed directly to the carry-in of
the next stage
For an n-bit ripple adder, it requires n full adders
Block diagram of 4 bit ripple adder
Truth table of ripple carry adderA1 A2 A3 A4 B4 B3 B2 B1 S4 S3 S2 S1 carry
0 0 0 0 0 0 0 0 0 0 0 0 0
0 1 0 0 0 1 0 0 1 0 0 0 0
1 0 0 0 1 0 0 0 0 0 0 0 1
1 0 1 0 1 0 1 0 0 1 0 0 1
1 1 0 0 1 1 0 0 1 0 0 0 1
1 1 1 0 1 1 1 0 1 1 0 0 1
1 1 1 1 1 1 1 1 1 1 1 0 1
DSCH SCHEMATIC
LAYOUT
AdvantagesWe can add two n-bit numbers easily
It is advantageous for less number of bit operations
top related