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Question
How would you set up a circuit to obtain NOT gate using a transistor?
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Solution
(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 VCC = V (Voltage corresponding to 1 state)
The resistors R and RB 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 |
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