Question

Write the truth table for circuit given in figure below consisting of NOR gates and identify the logic operation, $(OR,AND,NOT)$ which this circuit is performing.

Answer 1

Step 1: Find output for the given circuit.

Given, input for the circuit, $A$ and $B$
Output from the first $NOR$ gate is $\overline{A+B}$

The output from the first gate will be input for the second gate,

So, output of the circuit

$Y=\overline{\overline{A+B}+\overline{A+B}}$

$Y=\overline{\overline{A+B}}.\overline{\overline{A+B}}$

$Y=(A+B).(A+B)$

$Y=A+B$

This is the logic operation for $OR$ gate.

Step 2: Write truth table for the given circuit.

$\begin{array}{ccc}Input\left(A\right)& Input\left(B\right)& Output(Y=A+B)\\ 0& 0& 0\\ 0& 1& 1\\ 1& 0& 1\\ 1& 1& 1\end{array}$


Final answer: $OR$ gate.