NOT Gate
NOT gate inverts the signal, i.e., if input is 1 then output of NOT gate is 0 and for 0 input, the output is 1.
Truth Table
| A | Y |
| 0 | 1 |
| 1 | 0 |
The circuit to implement a NOT gate is identical to that used for a transistor as a switch.
When input A is at 0 level, transistor is off and the entire VCC voltage (5V) appears at the output Y. When input A is 1 (5V), the transistor conducts and output voltage Y is 0.