1. By
T.Mounika

2. 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).

3. 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

4. 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
3 inputs carry

5. 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

6. Ripple carry adder
The 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

7. Block diagram of 4 bit ripple adder

8. Truth table of ripple carry adder
A1 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

9. DSCH SCHEMATIC

11. LAYOUT

12. Advantages
We can add two n-bit numbers easily
It is advantageous for less number of bit operations