Digital Circuits Questions and Answers – Demultiplexers (Data Distributors) – 1

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Demultiplexers (Data Distributors) – 1”.

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

Answer: d
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:
A demultiplexer sends a single input to multiple outputs, depending on the select lines

2. 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
View Answer

Answer: a
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.

3. Most demultiplexers facilitate which type of conversion?
a) Decimal-to-hexadecimal
b) Single input, multiple outputs
c) AC to DC
d) Odd parity to even parity
View Answer

Answer: b
Explanation: A demultiplexer sends a single input to multiple outputs, depending on the select lines. Demultiplexer converts single input into multiple outputs.
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4. In 1-to-4 demultiplexer, how many select lines are required?
a) 2
b) 3
c) 4
d) 5
View Answer

Answer: a
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.

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

Answer: b
Explanation: A demultiplexer sends a single input to multiple outputs, depending on the select lines. As the select input changes, the output of the multiplexer varies according to that input.

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

Answer: b
Explanation: It can be calculated from the figure shown below:
The output is Y1 in 1-to-4 multiplexer if C1 = 0 & C2 = 1
For C0 =1 and C1 =0, Y1 will be the output as 0 and 1 are the bit combinations of 1.

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

Answer: d
Explanation: It can be calculated from the figure shown below:
The output is Y1 in 1-to-4 multiplexer if C1 = 0 & C2 = 1
For C0 =1 and C1 =0, Y3 will be the output as 0 and 1 are the bit combinations of 1.
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8. How many select lines are required for a 1-to-8 demultiplexer?
a) 2
b) 3
c) 4
d) 5
View Answer

Answer: b
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.

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

Answer: c
Explanation: The number of AND gates required will be equal to the number of outputs in a demultiplexer, which are 8.
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10. The output Q4 of this 1-to-8 demultiplexer is ____________
The output Q4 of the 1-to-8 demultiplexer
a) Q2.(Q1)’.Q0.I
b) Q2.Q1.(Q0)’.I
c) Q2.(Q1)’.(Q0)’.I
d) Q2.(Q1).Q0.I
View Answer

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

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

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

Sanfoundry Global Education & Learning Series – Digital Circuits.

To practice all areas of Digital Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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