Digital Circuits & Design, 1st Education by Pearson

5.8 | Chapter 5

5.2.1 | Half-Adder

Two single bits (binary digits) are added to produce sum and carry bits. Any overow

from rst bit into second bit is known as carry. Half-adder circuit performs addition of two

single bit values and produces single bit sum and a carry.

Let single-bit augend, x and addend, y. On addition, single bit binary sum, S and carry-

out an overow in second bit is obtained. There are two input binary variables; augend, x

and addend, y and two output binary variables as sum, S and carry, C. Two input variables

give 2

2

(=4) possible minterms. Truth table is constructed and is given in Table 5.4.

2

nd

bit 1

st

bit 2

nd

bit