(a) The truth table of a NOR gate is as given below:
When the two inputs of NOR gates are joined as shown in Fig (a) i.e.when A = B = 0 or A = B = 1, the above truth table of the NOR gate reduces to the one as given below:
It is the truth table of a NOT gate. Therefore, the given circuit carries out the logic operation of a NOT gate.
Refer to Fig (b). Here the out put of two NOT gates (obtained from NOR gates) are connected to NOT gate. In a NOT gate, the input gets inverted. Let \(\bar A\,\,and\,\,\bar B\) be the outputs of the two NOT gates. Now, the output of a NOR gate is 1 only when both the inputs are zero. Using this fact, the truth table for the given arrangement can be written as below:
It is the truth table of AND gate. Therefore, the given circuit acts as AND gate.
