The inverter (NOT circuit) performs a basic logic function called inversion or complementation. The purpose of the inverter is to change one logic level (HIGH / LOW) to the opposite logic level. In terms of bits, it changes a ‘1’ to a ‘0’ and vice versa. The standard logic symbol for the inverter and a Venn diagram illustrating the relationship between the variables and the logic gate operation, are shown in Figure 1-1 and Figure 1-2, respectively.
Figure 1-2 Venn diagram illustrating inverter operationFigure 1-1 Standard Logic Symbol for Inverter
We generally express the logical operation of a gate with a truth table which lists all input combinations and the corresponding outputs. The truth table for the NOT gate is shown in Table 1-1.
INPUT |
OUTPUT |
|---|---|
A |
|
0 |
1 |
1 |
0 |
Table 1-1Truth table for NOT gate
Note: The total number of possible input combinations (N) is determined by the mathematical formula:
(1-1)
where n is the number of input variables.
