Adder (electronics)

A full adder (English full adder ) is a switching network, commonly implemented as a digital circuit. It comprises three inputs ( X, Y and CIN) and two outputs (s and cout ). With a full adder can add three -digit binary numbers. Where s (English sum - sum) of the output provides the least significant digit of the result, the output cout ( engl. carry ( output) - carry ( output) ) the higher value. The identifier cin and cout basing it suggests a possibility of overflow treatment in Addiernetzen.

The following truth table illustrates the operation of a full adder:

This implies the following equations by first forming the disjunctive normal form of the truth values ​​of the table and then simplified:

And

The left figure shows the structure of a full adder using half-adders and an OR gate.

The right figure also shows the structure of a full adder, in which the half adder in each case were separated by an AND gate and an XOR gate. It should be noted that in both figures the sum outputs are each s down and cout the carry outputs of half adder shown above in each case.

The adder is used to build adders, often in combination with a half-adder.