GATE CS 1993 Q6.1 — Combinational Circuits

The given circuit consists of two inputs, $A$ and $B$, and performs the following operations:

1. The inputs $A$ and $B$ are passed through inverters to obtain $\bar{A}$ and $\bar{B}$ respectively.
2. One AND gate receives the direct inputs $A$ and $B$, producing the output: $$Y_1 = A \cdot B$$
3. Another AND gate receives the inverted inputs $\bar{A}$ and $\bar{B}$, producing the output: $$Y_2 = \bar{A} \cdot \bar{B}$$
4. The outputs of both AND gates are fed into a two-input OR gate, yielding the final output $Y$: $$Y = Y_1 + Y_2 = AB + \bar{A}\bar{B}$$

The Boolean expression $AB + \bar{A}\bar{B}$ represents the Exclusive-NOR (XNOR) logic function, which outputs $1$ when both inputs are equal.

Therefore, the correct option is B.