The GATE Grind

GATE 2015 EE – Question 25

Analog and Digital Electronics · VCOs and timers, combinatorial and sequential logic circuits, multiplexers, demultiplexers · 1 mark · Multiple choice

In the $4 \times 1$ multiplexer, the output F is given by $F = A \oplus B$. Find the required input '$I_3 I_2 I_1 I_0$'.

A 4 x 1 multiplexer with data inputs $I_0$ to $I_3$, select inputs $S_1 = A$ and $S_0 = B$, and output F.
  1. 1010
  2. 0110
  3. 1000
  4. 1110

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) 0110

Explanation

With $S_1 S_0 = AB$, the input $I_k$ is chosen when $AB = k$. So $I_0 = F(0,0) = 0$, $I_1 = F(0,1) = 1$, $I_2 = F(1,0) = 1$ and $I_3 = F(1,1) = 0$. The inputs $I_3 I_2 I_1 I_0$ are 0110.