Full Adder Using Two Half Adder Circuit Diagram. Similarly the expression for carry output can be rewritten as follows. Finally the output s is obtained.
The expressions for sum and carry outputs can be rewritten as follows. A full adder can be formed by logically connecting two half adders. The first half adder circuit will be used to add a and b to produce a partial sum.
If any of the half adder logic produces a carry there will be an output carry.
The circuit diagram for this can be drawn as and it could be represented in block diagram as the boolean expression for sum and carry is as sum a b c carry ab a b. Figure shows the logic circuit diagram of the full adder. Cout ab acin bcin. Thus we can implement a full adder circuit with the help of two half adder circuits.
