oR Gate
An oR gate produces a 1 output if any of its inputs are 1s. The output is a 0 if all the inputs are 0s. The output of a two-input OR gate is shown in the truth table in Figure 42-3. The total number of possible combinations is expressed by N 5 22 5 4. The truth table shows all four combinations.
An OR gate performs the basic operation of addition. The algebraic expression for the output of an OR gate is Y 5 A 1 B. The plus sign designates the oR function.
Figure 42-4 shows the logic symbol for an OR gate. The inputs are labeled A and B, and the output is
Questions
1. What conditions produce a 1 output for an OR gate?
2. Draw the symbol used to represent a two-input OR gate.
3. Develop a truth table for a three-input OR gate.
4. What operation is performed by an OR gate?
5. What algebraic expression represents the output of an OR gate?