Question

How would you set up a circuit to obtain NOT gate using a transistor?

Answer 1

(1) It has only one input and only one output.

(2) Boolean expression is Y = Ᾱ and is read as “y equals not A”.

Logical symbol of NOT gate.

(3) Realization of NOT gate: The transistor is so biased that the collector voltage V_CC = V (Voltage corresponding to 1 state)

The resistors R and R_B are so chosen that if the input is low, i.e. 0, the transistor is in the cut-off and hence the voltage appearing at the output will be the same as applied V = 5 V. Hence Y = V (or state I)

If the input is high, the transistor current is in saturation and the net voltage at the output Y is 0 (in state 0).

(4) Truth table for NOT gate:

A	Y = Ā
0	1
1	0