Defined as :
It is a logic circuit which performs the arithmetic sum of the three input bits i.e. addend bit,augend bit and a carry bit .
It has three input and two output. A, B and CIN as inputs and S, COUT as outputs.
Truth table for full adder
Boolean expression for Sum and Carry out can be derived using K – Map.
k map for SUM is below,
therefore,the simplified expression for sum is,
so, here we need four 3-input AND gate and one 4-input OR gate to design circuit for SUM.
Now ,the k-map for carry out is
and the simplified expression results for carry out is,
Similarly,we required three 2-input AND gate and one 3-input OR gate for carry circuit.
LOGIC EXPRESSION for full adder
two level realization of FULL ADDER shown below,
we need two EXOR gates and 3 (two- input AND gate)with one (three -input OR gate) for designing full adder.Here the circuit diagram for full adder,
LOGIC SYMBOL for full adder
FULL ADDER USING TWO HALF ADDERS logic diagram