# Digital Circuits Questions and Answers – Demultiplexers (Data Distributors)

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Demultiplexers (Data Distributors)

1. In 1-to-4 multiplexer, if C1 = 0 & C2 = 1, then the output will be ___________
a) Y0
b) Y1
c) Y2
d) Y3

Explanation: It can be calculated from the figure shown below: For C0 =1 and C1 =0, Y1 will be the output as 0 and 1 are the bit combinations of 1.

2. In 1-to-4 multiplexer, if C1 = 1 & C2 = 1, then the output will be ___________
a) Y0
b) Y1
c) Y2
d) Y3

Explanation: It can be calculated from the figure shown below: For C0 =1 and C1 =0, Y3 will be the output as 0 and 1 are the bit combinations of 1.

3. How many select lines are required for a 1-to-8 demultiplexer?
a) 2
b) 3
c) 4
d) 5

Explanation: The formula for total no. of outputs is given by 2n, where n is the no. of select lines. In this case n = 3 since 23 = 8.

4. How many AND gates are required for a 1-to-8 multiplexer?
a) 2
b) 6
c) 8
d) 5

Explanation: The number of AND gates required will be equal to the number of outputs in a demultiplexer, which are 8.

5. The output Q4 of this 1-to-8 demultiplexer is ____________ a) Q2.(Q1)’.Q0.I
b) Q2.Q1.(Q0)’.I
c) Q2.(Q1)’.(Q0)’.I
d) Q2.(Q1).Q0.I

Explanation: The output Y4 = Q2.(Q1)’.(Q0)’.I. since the bit combinations of 4 are 100.

6. Which IC is used for the implementation of 1-to-16 DEMUX?
a) IC 74154
b) IC 74155
c) IC 74139
d) IC 74138

Explanation: IC 74154 is used for the implementation of 1-to-16 DEMUX, whose output is inverted input.

7. The word demultiplex means ___________
a) One into many
b) Many into one
c) Distributor
d) One into many as well as Distributor

Explanation: The word demultiplex means “one into many” and distributor. A demultiplexer sends a single input to multiple outputs, depending on the select lines. It is clear from the diagram: 8. Why is a demultiplexer called a data distributor?
a) The input will be distributed to one of the outputs
b) One of the inputs will be selected for the output
c) The output will be distributed to one of the inputs
d) Single input to Single Output

Explanation: A demultiplexer sends a single input to multiple outputs, depending on the select lines. For one input, the demultiplexer gives several outputs. That is why it is called a data distributor.

9. Most demultiplexers facilitate which type of conversion?
b) Single input, multiple outputs
c) AC to DC
d) Odd parity to even parity

Explanation: A demultiplexer sends a single input to multiple outputs, depending on the select lines. Demultiplexer converts single input into multiple outputs.

10. In 1-to-4 demultiplexer, how many select lines are required?
a) 2
b) 3
c) 4
d) 5

Explanation: The formula for total no. of outputs is given by 2n, where n is the no. of select lines. Therefore, for 1:4 demultiplexer, 2 select lines are required.

11. In a multiplexer the output depends on its ___________
a) Data inputs
b) Select inputs
c) Select outputs
d) Enable pin

Explanation: Depending on the select lines, a demultiplexer provides a single input to multiple outputs. The output of the multiplexer varies according to the select input as it changes.

The demultiplexer is a logic device that switches one common input line to one of numerous different output lines. The data distributor, often known as a Demultiplexer or simply “Demux,” is the polar opposite of the Multiplexer we examined earlier. A demultiplexer is a device that allows a single source to be connected to multiple destinations. Demultiplexers are most commonly utilised in communication systems that utilise multiplexers. The majority of communication systems are bidirectional, meaning they work in both directions (transmitting and receiving signals). Depending on the select lines, a demultiplexer provides a single input to multiple outputs. The output varies as the choose input changes.