Half Adder and Full Adder

HALF ADDER:

•               Design a logic circuit to add two bits and produce a sum bit and a carry bit. Two inputs and two outputs are needed. Let us call the inputs x and y, and the outputs S and C.

•               A half adder

–   For adding 2 bits

–   Gives “carry out” and “sum”

–   1 AND and 1 XOR gate

FULL-ADDER:

Adding two single-bit binary values, X, Y with a carry input bit C-in produces a sum bit S and a carry out C-out bit.

•               A full adder

–   For adding 2 bits plus a “carry in”

–   Gives “carry out” and “sum”

–   2 ANDs, 2 XORs, and 1 OR

FULL ADDER CIRCUIT USING AND-OR:

FULL ADDER CIRCUIT USING XOR: