GATE 2022 EC – Question 19

Digital Circuits · Combinatorial Circuits · 1 mark · Multiple choice

Consider the 2-bit multiplexer (MUX) shown in the figure. For OUTPUT to be the XOR of C and D, the values for $A_0$, $A_1$, $A_2$, and $A_3$ are ________.

Diagram for GATE 2022 EC question 19

$A_0=0,\ A_1=0,\ A_2=1,\ A_3=1$
$A_0=1,\ A_1=0,\ A_2=1,\ A_3=0$
$A_0=0,\ A_1=1,\ A_2=1,\ A_3=0$
$A_0=1,\ A_1=1,\ A_2=0,\ A_3=0$

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) $A_0=0,\ A_1=1,\ A_2=1,\ A_3=0$

Explanation

The select lines are $S_1=C$ and $S_0=D$, so input $A_{2C+D}$ is passed to the output. XOR is 0 for $CD=00$, 1 for $01$, 1 for $10$, 0 for $11$. Hence $A_0=0$, $A_1=1$, $A_2=1$, $A_3=0$.