A digital logic circuit can be realized completely by the repeated usage of which universal logic gate?
Both NAND and NOR logic gates are universal gates because any Boolean expression can be constructed using only NAND gates or only NOR gates.
An OR gate has 4 input signals. How many rows will be present in its truth table?
For an n-input logic gate, total truth table combinations equal $2^n$. For $n = 4, 2^4 = 16 rows$.
What is De Morgan's theorem primarily used for in digital circuit design?
De Morgan's theorems ((A.B)' = A' + B' and (A+B)' = A'.B') enable simplification and conversion between logic expressions.
Simplify the Boolean expression: A + A'B
$Using distributive law: A + A'B = (A + A')(A + B) = (1)(A + B) = A + B.$
What is the Boolean expression for an XOR gate with inputs A and B?
The output of a 2-input XOR gate is HIGH when the inputs are different: Y = A'B + AB' (or A XOR B).