Digital Logic Design : 09/22/14

Students, you have to write this Expt in your RECORD.

Dont write the Eeperiment Number.

EXPERIMENT: 9 HALF ADDER AND FULL ADDER

AIM: To realize Half Adder and Full Adder using Basic gates

LEARNING OBJECTIVE:

_ To realize the half adder circuits using basic gates

_ To realize full adder using two half adders

COMPONENTS REQUIRED:

IC 7408, IC 7486, IC 7432, Patch Cords & IC Trainer Kit.

THEORY:

Adder circuit is a combinational digital circuit that is used for adding two numbers. A typical adder circuit produces a sum bit (denoted by S) and a carry bit (denoted by C) as the output. Typically adders are realized for adding binary numbers but they can be also realized for adding other formats like BCD (binary coded decimal, XS-3 etc. Besides addition, adder circuits can be used for a lot of other applications in digital electronics like address decoding, table index calculation etc. Adder circuits are of two types: Half adder ad Full adder.

Half-Adder: A combinational logic circuit that performs the addition of two data bits, A and

B, is called a half-adder. Addition will result in two output bits; one of which is the sum bit, S, and the other is the carry bit, C. The Boolean functions describing the half-adder are: S =A Å B C = A B

Full-Adder: The half-adder does not take the carry bit from its previous stage into account. This carry bit from its previous stage is called carry-in bit. A combinational logic circuit that adds two data bits, A and B, and a carry-in bit, Cin , is called a full-adder. The Boolean functions describing the full-adder are:

S = (x Å y) Å Cin C = xy + Cin (x Å y)

Half adder circuit diagram: