Adders in Digital Logic
Definition of Half Adder A half adder is a logic circuit that adds two bits. It generates two outputs: SUM and CARRY. The boolean equations for SUM and CARRY are: Equation SUM = A ⊕ B = A'B + AB' CARRY = A . B Truth Table A B CARRY SUM 0 0 0 0 0 1 0 1 1 0 0 1 1 1 1 0 Following is the logic circuit diagram for half adder: Circuit Diagram Definition of Full Adder A full adder is a logic circuit that adds three bits. It generates two outputs: SUM and CARRY. Equation SUM = A ⊕ B ⊕ C = (A'B'C + A'BC' + AB'C' + ABC) CARRY = AB + BC + CA Truth Table A B C CARRY SUM 0 0 0 0 0 0 0 1 0 1 0 1 0 0 1 0 1 1 1 0 1 0 0 0 1 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 Circuit Diagram