The output of an OR gate is high IF either input, A or B, or both, are in the high logic level. Figure 1 shows the symbol and the equivalent circuits.
Figure 1
Equation 1
2-Input OR gate
X = A + B
Where:
X is the input logic level
A and B are the output logic levels
Equation 2
3-Input OR Gate
X – A + B + C
Where:
X is the input logic level
A, B and C are the output logic levels
Truth Table
