NOT gate performs the inversion operation. This is also know as complemented. It change high logic level into low logic level or vice versa. This is a single input gate . the output Y can be expressed in terms of inputs as
Y = A -
Where A represents NOT operation. If input a NOT gate is A then out put will be A ( it is pronounced as A bar) the logical symbol and truhtabel of not gate are shown in fig.
Figure (a) symbol and (b) truth table of not gate