Multiplexer MCQ Quiz - Objective Question with Answer for Multiplexer - Download Free PDF

Last updated on Jul 9, 2025

Latest Multiplexer MCQ Objective Questions

Multiplexer Question 1:

In the context of MUX applications, what does a MUX allow in terms of control?

  1. It amplifies the signal before sending it to the output.
  2. It generates clock pulses for digital circuits. 
  3. It performs arithmetic operations on multiple data inputs.
  4. It allows control of multiple inputs to a single output based on select lines.

Answer (Detailed Solution Below)

Option 4 : It allows control of multiple inputs to a single output based on select lines.

Multiplexer Question 1 Detailed Solution

Multiplexer:

  • A multiplexer (MUX) is a combinational logic circuit designed to switch one of several inputs to a single common output line.
  • A multiplexer is Many to One data selector
  • A multiplexer selects one of the many data available at its input depending on the bits on the select line
  • For 2n inputs, there are n select lines that determine, which input is to be connected to the output.

 

Example:

A 4-input multiplexer is as shown below.

Output, Y = I010 + I11S0 + I2S10 + I3S1S0

Multiplexer Question 2:

For a 2-to-1 Multiplexer with inputs I0 = 0, I1 = 1, and select line S = 1, what is the value of the output Y?

  1. 0
  2. 0.5
  3. 1
  4. Undefined

Answer (Detailed Solution Below)

Option 3 : 1

Multiplexer Question 2 Detailed Solution

Explanation:

A 2-to-1 multiplexer is a combinational logic circuit that selects one of the two input signals (I0 or I1) and forwards it to a single output (Y), based on the value of the select line (S). The operation of the multiplexer is controlled by the binary value of the select line. A multiplexer is often referred to as a "data selector" because it selects one input to pass to the output.

Working Principle: The 2-to-1 multiplexer works as follows:

  • When the select line (S) is 0, the output (Y) is equal to the input I0.
  • When the select line (S) is 1, the output (Y) is equal to the input I1.

The logical expression for the output (Y) of a 2-to-1 multiplexer can be written as:

Y = (S' × I0) + (S × I1)

Here:

  • S' is the complement of the select line S.
  • × represents the logical AND operation.
  • + represents the logical OR operation.

Correct Option Analysis:

Let us solve the problem step-by-step to determine the correct output for the given inputs:

Given:

  • Input I0 = 0
  • Input I1 = 1
  • Select line S = 1

Using the logical expression for the output of a 2-to-1 multiplexer:

Y = (S' × I0) + (S × I1)

Step 1: Find the complement of S (S'):

Since S = 1, the complement of S (S') is:

S' = 0

Step 2: Calculate the first term (S' × I0):

Substitute S' = 0 and I0 = 0 into the expression:

S' × I0 = 0 × 0 = 0

Step 3: Calculate the second term (S × I1):

Substitute S = 1 and I1 = 1 into the expression:

S × I1 = 1 × 1 = 1

Step 4: Add the two terms to find the output Y:

Y = (S' × I0) + (S × I1)

Substitute the values:

Y = 0 + 1 = 1

Therefore, the output of the 2-to-1 multiplexer is:

Y = 1

Correct Option:

The correct option is Option 3: 1

Multiplexer Question 3:

A combinational logic circuit that is used when it is desired to send data from two or more source through a single transmission line is known as _________. 

  1. Encoder
  2. Multiplexer
  3. Decoder
  4. More than one of the above
  5. None of the above

Answer (Detailed Solution Below)

Option 2 : Multiplexer

Multiplexer Question 3 Detailed Solution

Encoder:

An encoder has 2n input lines and n output lines. In the encoder, the output lines generate the binary code corresponding to the input value which is active high.

Decoder:

It is a multi-input and multi-output logic circuit that converts coded inputs into coded outputs where input and output codes are different. Input code has fewer bits than output code. There is one to one mapping from input to output.

Multiplexer:

It is a digital switch. It allows digital information from several sources to be routed onto a single output line. A basic multiplexer has several data input lines and a single output line. The selection of a particular input line is controlled by selection lines. It is many to one mapping and provides the digital equivalent of an analog selector switch. Therefore it is the correct answer

Demultiplexer:

It is a circuit that receives information on a single line and transmits information on one of the 2n output lines. Selection of output line is controlled by values of n selection lines. 

Multiplexer Question 4:

Minimum number of 2 : 1 multiplexer required to design a 16 : 1 multiplexer is _______

  1. 8
  2. 4
  3. 15
  4. More than one of the above
  5. None of the above

Answer (Detailed Solution Below)

Option 3 : 15

Multiplexer Question 4 Detailed Solution

To implement 2n × 1 MUX using 2 × 1 MUX, the total number of 2 × 1 MUX required is (2n - 1).

∴ The number of 2 × 1 multiplexer required to implement 16 × 1 MUX will be:

n = 16 - 1 = 15

Or we can follow the below steps to calculate the same:

1st stage 

2nd  stage 

3rd stage 

4th stage 

The sum will give the total number of MUX required to implement 16 × 1 multiplexer using 2 × 1, i.e.

n = 8 + 4 + 2 + 1 = 15

Given MUX

To be implemented

Required

2 : 1

16 : 1

8 + 4 + 2 + 1 = 15

4 : 1

16 : 1

4 + 1 = 5

4 : 1

64 : 1

16 + 4 + 1 = 21

8 : 1

64 : 1

8 + 1 = 9

8 : 1

256 : 1

32 + 4 + 1 = 37

Multiplexer Question 5:

Minimum number of 2 : 1 multiplexer required to design a 16 : 1 multiplexer is _______

  1. 8
  2. 4
  3. 15
  4. 10
  5. 16

Answer (Detailed Solution Below)

Option 3 : 15

Multiplexer Question 5 Detailed Solution

To implement 2n × 1 MUX using 2 × 1 MUX, the total number of 2 × 1 MUX required is (2n - 1).

∴ The number of 2 × 1 multiplexer required to implement 16 × 1 MUX will be:

n = 16 - 1 = 15

Or we can follow the below steps to calculate the same:

1st stage 

2nd  stage 

3rd stage 

4th stage 

The sum will give the total number of MUX required to implement 16 × 1 multiplexer using 2 × 1, i.e.

n = 8 + 4 + 2 + 1 = 15

Given MUX

To be implemented

Required

2 : 1

16 : 1

8 + 4 + 2 + 1 = 15

4 : 1

16 : 1

4 + 1 = 5

4 : 1

64 : 1

16 + 4 + 1 = 21

8 : 1

64 : 1

8 + 1 = 9

8 : 1

256 : 1

32 + 4 + 1 = 37

Top Multiplexer MCQ Objective Questions

A 4 × 1 Multiplexer is shown in the Figure below. The output Z is

  1. A NOR C
  2. B NOR C
  3. B XOR C
  4. A XOR C

Answer (Detailed Solution Below)

Option 4 : A XOR C

Multiplexer Question 6 Detailed Solution

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Concept:

 

In a 4 × 1 MUX

Truth-Table is given as:

S1

S0

V

0

0

I0

0

1

I1

1

0

I2

1

1

I3

 

Y = Output = S̅0 I0 + S̅1 S0 I1 + S1 S̅0 I2 + S1 S0 I3

MUX contains AND gate followed by OR gate

Calculation:

Given:

Z = Output = A̅B̅C + A̅BC + AB̅C̅ + ABC̅ 

Z = A̅C(B̅ + B) + AC̅(B̅ + B)

Z = A̅C + AC̅

Z = A XOR C

Hence, option 4 is correct.

The Boolean expression for the output f of the multiplexer shown below is

  1. P ⊕ Q ⊕ R
  2. P + Q + R

Answer (Detailed Solution Below)

Option 2 : P ⊕ Q ⊕ R

Multiplexer Question 7 Detailed Solution

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The correct answer is option 2.

Concept:

In a 4 × 1 MUX

Truth-Table is given as:

S1

S0

V

0

0

I0

0

1

I1

1

0

I2

1

1

I3

 

Y = Output = S̅0 I0 + S̅1 S0 I1 + S1 S̅0 I2 + S1 S0 I3

MUX contains AND gate followed by OR gate

Calculation:

Given:

Z = Output = P̅Q̅R + P̅QR̅ +PQ̅ R̅ + PQR

Z = P̅(Q̅R + QR̅ ) +P(Q̅ R̅ + QR)

Z =

Z = P ⊙ Q ⊙ R = P ⊕ Q ⊕ R

Digital multiplexer is basically a combinational logic circuit to perform the operation 

  1. AND-AND
  2. OR-OR
  3. AND-OR
  4. OR-AND

Answer (Detailed Solution Below)

Option 3 : AND-OR

Multiplexer Question 8 Detailed Solution

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Multiplexers:

  • A multiplexer is a combinational circuit.
  • A multiplexer is Many to one data selector.
  • A multiplexer selects one of the many data available at its input depending on the bits on the select line.
  • For 2n inputs, there are n select lines that determine, which input is to be connected to the output.

Example:

A 4-input multiplexer is as shown below.

Output, Y = I010 + I11S0 + I2S10 + I3S1S0

The output of a 4-input multiplexer represents one combinational functions of 3-variables each.

The function can be seen as a combination of AND-OR functions. (Sum of products)

For a design of (16 ∶ 1) multiplexer, how many select lines will be required?

  1. 1
  2. 3
  3. 4
  4. 2

Answer (Detailed Solution Below)

Option 3 : 4

Multiplexer Question 9 Detailed Solution

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Concept:

Multiplexer: 

  • A multiplexer is Many to one data selector.
  • A multiplexer selects one of the many data available at its input depending on the bits on the select line.
  • For selecting eight inputs, there are three data select lines that must be used. The multiplexer requires the data select lines. We have three data select lines for eight inputs, and it's an 8:1 multiplexer.

Example:

The 16 × 1 multiplexer selects one of the 8 inputs and presents it to the output, i.e.
2m  = 16
m = log2 16 = log2 (24)
m = 4log2 2
m = 4

So, the number of data select lines is 4.

In a multiplexer, if there are 4 input lines and 1 output line, then number of selection lines will be: 

  1. 3
  2. 0
  3. 2
  4. 1

Answer (Detailed Solution Below)

Option 3 : 2

Multiplexer Question 10 Detailed Solution

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Concept:

The number of selection line is n for n bit resistor in multiplexer:

No. selection line in MUX = log2 n

In the destination decoder,

No. of selection line = log2 n

Analysis:

Given:

Mux is 4 x 1

So, n = 4 

No. of the selection line in MUX = log2

No. of the selection line in decoder = log2 4 = 2 bit

Option (3) is the correct choice.

Important Points

More information about MUX:

1) It is a data selector combinational circuit.

2) It is many to-one, parallel to serial convertor

3) It is also called universal logic circuit

4) MUX contain AND gate followed by OR gate

The minimum Boolean expression for the following circuit is

  1. AB + AC + BC

  2. A + BC
  3. A + B
  4. A + B + C

Answer (Detailed Solution Below)

Option 1 :

AB + AC + BC

Multiplexer Question 11 Detailed Solution

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A(B + C) + AB + (A + B)C

= AB + AC + AB + AC + BC

= AB + AC + BC

Without any additional circuitry, a 16:1 MUX can be used to obtain

  1. Only some Boolean functions of 4 variables
  2. All Boolean functions of 4 variables
  3. Only some Boolean functions of 3 variables
  4. All Boolean functions of 5 variables

Answer (Detailed Solution Below)

Option 2 : All Boolean functions of 4 variables

Multiplexer Question 12 Detailed Solution

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Concept:

  • A multiplexer with n-data select inputs can implement any function of n-variables and some function of (n + 1) variables.
  • The key to this design is to use the most significant input variable and its complement to drive some of the data inputs.

Calculation:

Given 16:1 MUX, i.e. 24:1 MUX,

Here, we have 4 data select lines.

So, without any additional circuitry, this given MUX can be used to obtain all Boolean functions of 4 variables and some Boolean functions of 4 + 1 = 5 variables.

The device which changes from serial data to parallel data is: 

  1. Demultiplexer
  2. Multiplexer
  3. Flip-Flop
  4. Counter

Answer (Detailed Solution Below)

Option 1 : Demultiplexer

Multiplexer Question 13 Detailed Solution

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The correct option is 1

Concept:

De-multiplexer:

  • The demultiplexer is a combinational logic circuit designed to switch one common input line to one of several separate output lines.
  • The data distributor, known as a Demultiplexer or “Demux”, works in just the opposite way to that of the Multiplexer.
  • The demultiplexer takes one single input data line and then switches it to any one of several individual output lines one at a time.

The block diagram is as shown:

Application:

The de-multiplexer converts a serial data signal at the input to parallel data at its output lines as shown below.

The function of the De-multiplexer is to switch one common data input line to any one of the 4 output data lines A to D.

Important:

Multiplexer:

The multiplexer is a combinational logic circuit designed to switch one of several input lines to a single common output line.

  • The multiplexer or “MUX” is a combinational logic circuit designed to switch one of several input lines through a single common output line by the application of a control signal.
  • Multiplexers operate like very fast-acting multiple-position rotary switches connecting or controlling multiple input lines called “channels” one at a time to the output.
  • Multiplexers are used to convert parallel to serial data.

Consider the following combinational function block involving four Boolean variables x, y, a, b where x, a, b are inputs and y is the output.

f (x, y, a, b)

(

                if (x is 1) y = a;

                else y = b;

}

Which one of the following digital logic blocks is the most suitable for implementing this function?

  1. Full adder
  2. Priority encoder
  3. Multiplexer
  4. Flip-flop

Answer (Detailed Solution Below)

Option 3 : Multiplexer

Multiplexer Question 14 Detailed Solution

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Set of inputs = {x, a, b}

Set of output = y

Also, the selection of a or b for output is dependent on value of x.

if x = 1, y = a

if x = 0, y = b

Hence, x acts as a selects the value. Therefore, this resembles a 2-to-1 MUX or 2-input Multiplexer.

Which of the following is a combinational logic circuit that has 2n input lines and a single output line?

  1. Demultiplexer
  2. Decoder
  3. Encoder
  4. Multiplexer

Answer (Detailed Solution Below)

Option 4 : Multiplexer

Multiplexer Question 15 Detailed Solution

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Multiplexer:

  • A multiplexer (MUX) is a combinational logic circuit designed to switch one of several inputs to a single common output line.
  • A multiplexer is Many to One data selector
  • A multiplexer selects one of the many data available at its input depending on the bits on the select line
  • For 2n inputs, there are n select lines that determine, which input is to be connected to the output.

 

Example:

A 4-input multiplexer is as shown below.

Output, Y = I010 + I11S0 + I2S10 + I3S1S0

The output of 4-input multiplexer represents one combinational functions of 3-variables each.

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