Question

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

Answer 1

Here the base $B$ of the transistor is connected to the input A through to the input A through the input resistance $R_B$ and the emitter is earthed. The collector is connected to $5V$ battery. The output $Y$ is the voltage at $C$ w.r.t earth.

The resistance $R_B$ and $R_C$ are base and collector resistors such that if emitter-base junction is unbiased, the transistor is in cut-off region and if emitter-base is in forward bias by $5V$ at $A$, the transistor is in saturation state.

$\begin{array}{cc}\text{Input}& \text{Output}\\ A& A\\ 0& 1\\ 1& 0\end{array}$

The $NOT$ gate is a device which has only one input and one output i.e., $Y=\overline{A}$ means, $Y$ equals to $NOTA$.

$\text{Final Answer}$

$\begin{array}{cc}\text{Input}& \text{Output}\\ A& A\\ 0& 1\\ 1& 0\end{array}$