CMOS Half adder :

The truth table of the half adder is as shown in Table below

By using the 'k' map the Boolean function of sum can be derived as,

Similarly by using 'k' map the Boolean function of carry can be derived as,

Now by observing the Boolean expression of sum and carry it can be seen that the Boolean expression of sum = – A B + A– B is the XOR gate and the carry = AB is the AND gate. The complete CMOS realization of the half adder is as shown in Figure below