Sequential Circuits MCQ Quiz - Objective Question with Answer for Sequential Circuits - Download Free PDF

Last updated on May 30, 2025

Latest Sequential Circuits MCQ Objective Questions

Sequential Circuits Question 1:

In an asynchronous counter, the clock input of each flip-flop except first flip-flop is connected to:

  1. the same clock source
  2. the output of the previous flip-flop
  3. a separate clock source
  4. a common reset line

Answer (Detailed Solution Below)

Option 2 : the output of the previous flip-flop

Sequential Circuits Question 1 Detailed Solution

The correct answer is: 2) the output of the previous flip-flop

Explanation:
In an asynchronous counter (also called a ripple counter):

Only the first flip-flop receives the external clock signal.

Each subsequent flip-flop is triggered by the output (Q or Q̅) of the previous flip-flop, not by a common clock.

This causes a ripple effect, where changes propagate sequentially, leading to a slight delay between stages.

Additional Information
Asynchronous Counter

Asynchronous counters are those counters where the clock of the next stage is obtained from the output of the previous state.

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Sequential Circuits Question 2:

A positive edge-triggered T Flip-Flop has T = 1. If the current output Q is 0, what will be the output Q after 3 clock pulses?

  1. 0
  2. Unchanged
  3. 1
  4. Toggles

Answer (Detailed Solution Below)

Option 3 : 1

Sequential Circuits Question 2 Detailed Solution

The correct answer is option 3) 1

Concept:

Let's analyze the given problem statement and options in detail:

Given:

  • T = 1
  • Current output Q = 0

Let's analyze the state of Q after each clock pulse:

  1. Initial state Q = 0
  2. After 1st clock pulse: Q will toggle from 0 to 1
  3. After 2nd clock pulse: Q will toggle from 1 to 0
  4. After 3rd clock pulse: Q will toggle from 0 to 1

Therefore, the output Q after 3 clock pulses will be 1.

Sequential Circuits Question 3:

How many clock pulses are required to load n bits into an n-bit SIPO shift register?

  1. n2
  2. 2n
  3. n
  4. 2n

Answer (Detailed Solution Below)

Option 3 : n

Sequential Circuits Question 3 Detailed Solution

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Concept:

Serial input serial output:

F5 Madhuri Engineering 09.06.2022 D5

SISO is used to provide 'n' clock pulses delay to the input data 

If 'T' is clock pulses time period then  delay provided by n bit SISO is "nT"

n bit register to enter n bit data it required n clock pulses in serial form.

Output is taken serially than (n-1) clock pulses are required

Sequential Circuits Question 4:

What is the correct sequence of steps used by knowledge base designing?

A. Ask questions about the intended interpretation.

B. Chose task domain or world to represent.

C. Select atoms to represent propositions of Interest.

D. Tells the system propositions that are true in the intended interpretation/axiomatizing the domain.

Choose the correct answer from the options given below:

  1. A, B, C, D
  2. B, C, D, A
  3. C, D, A, B
  4. D, A, B, C

Answer (Detailed Solution Below)

Option 2 : B, C, D, A

Sequential Circuits Question 4 Detailed Solution

The correct answer is Option 2.

Key Points

  • Knowledge base designing involves a specific sequence of steps to accurately represent a domain of interest.
    • A. Ask questions about the intended interpretation: This step involves understanding the context and the specific meanings of the propositions that will be represented in the knowledge base.
    • B. Choose task domain or world to represent: This step involves selecting the particular area or world that the knowledge base will cover.
    • C. Select atoms to represent propositions of interest: In this step, the basic atomic elements or propositions that are relevant to the domain are identified.
    • D. Tell the system propositions that are true in the intended interpretation/axiomatizing the domain: This step involves defining the truths or axioms that apply to the chosen domain.

The correct sequence of these steps is:

  1. B. Choose task domain or world to represent.
  2. C. Select atoms to represent propositions of interest.
  3. D. Tell the system propositions that are true in the intended interpretation/axiomatizing the domain.
  4. A. Ask questions about the intended interpretation.

Hence, the correct answer is Option 2.

Additional Information

  • The steps in knowledge base designing ensure that the system accurately represents the chosen domain and can effectively interpret and answer queries.
  • Each step builds upon the previous ones, creating a robust and reliable knowledge base.
  • Properly asking questions about the intended interpretation helps in refining the knowledge base and ensuring it accurately reflects the domain.

Sequential Circuits Question 5:

In a shift register, if a binary number 1101 is initially stored and the register is made to shift two times to the right, which of the following would be the content of the register? 

  1. 0110 
  2. 1101 
  3. 0011 
  4. 1110

Answer (Detailed Solution Below)

Option 3 : 0011 

Sequential Circuits Question 5 Detailed Solution

Concept:

Right Shift Register:

60d6f81a96904e47c86f8f5e 16377327504661

  • The shift register, which allows serial input (one bit after the other through a single data line) and produces a serial output is known as Serial-In Serial-Out shift register.
  • Since there is only one output, the data leaves the shift register one bit at a time in a serial pattern, thus the name Serial-In Serial-Out Shift Register.

Solution:

Pulse Q3 Q2 Q1 Q0
0-pulse 1 1 0 1
1-pulse 0 1 1 0
2-pulse 0 0 1 1

Top Sequential Circuits MCQ Objective Questions

The S-R latch is an example of:

  1. Combinational circuit
  2. Synchronous sequential circuit
  3. One-bit memory element
  4. One-clock delay element

Answer (Detailed Solution Below)

Option 3 : One-bit memory element

Sequential Circuits Question 6 Detailed Solution

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Explanation:

Latches and Flip-Flop:

  • Latches and flip-flops are the basic elements to store 1-bit of data. Hence they are also known as a one-bit memory element.
  • Latches change the output continuously when there is a change in the input, i.e. they are level triggered.
  • Flip-flop is a combination of latch and clock. It changes the output that is adjusted by the clock.
  • The main difference between a latch and a flip-flop is that a flip-flop has a clock signal, whereas a latch does not.
  • We can say that a flip-flop without a clock is a latch.
  • Latches are asynchronous, which means that the output of a latch depends on its input.
  • Basically, there are 4 types of latches: SR latch, JK latch, D latch, T latch.

How many input terminal is represented by T flip flop? 

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

Answer (Detailed Solution Below)

Option 4 : 1

Sequential Circuits Question 7 Detailed Solution

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T flip flop

tff

The "T Flip Flop" has only one input.

It has only two output states i.e. hold and toggle.

For T = 0, the output is Q(Hold state)

For T = 1, the output is \(\overline{Q_n}\) (Toggle state)

The output equation of the T flip-flop is:

Qn+1 = T ⊗ Qn

T

Qn+1

0

No change

1

Toggle

Number of unused states in a 4 bit-Johnson counter are:

  1. 2
  2. 4
  3. 8
  4. 12

Answer (Detailed Solution Below)

Option 3 : 8

Sequential Circuits Question 8 Detailed Solution

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Concept:

A Johnson counter is a modified ring counter, where the inverted output from the last flip flop is connected to the input to the first.

The MOD of the Johnson counter is 2n if n flip-flops are used.

The circuit diagram for a 4-bit Johnson Counter is as shown:

D2

Calculation:

Total number of states in 4-bit counter are: 2n = 24 = 16

Total states in Johnson counter are: 2n = 2.(4) = 8

Unused states are 16 - 8 = 8

In a J-K flip-flop, if J = K̅, then it acts as a/an:

  1. T flip-flop
  2. D flip-flop
  3. RS flip-flop
  4. Decoder

Answer (Detailed Solution Below)

Option 2 : D flip-flop

Sequential Circuits Question 9 Detailed Solution

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D flip flop:

D flip flop has only one input terminal. The output of the D flip flop will be the same as the input. Hence, it is used in delay circuits.

The circuit is as shown below.

Logic symbol:

F1 U.B Madhu 27.03.20 D9

Truth table:

D

Qn 

(Present state)

Qn+1 

(Next state)

0

0

0

0

1

0

1

0

1

1

1

1

 

Characteristic equation: Qn+1 = D

The D flip flop may be obtained from an S-R flip flop by just putting one inverter between the S and R as shown in the figure below.

S = R̅

F1 U.B Madhu 27.03.20 D10

The D flip flop may be obtained from a J-K flip flop by just putting one inverter between the J and K as shown in the figure below.

K = J̅

F1 U.B Madhu 27.03.20 D11

T flip flop:

T flip flop has only one input terminal. The output of the T flip flop will be toggled when the input is high on every new clock pulse. The output will be the same as the previous state when the input is low.

The circuit is as shown below.

Logic symbol:

F1 U.B Madhu 27.03.20 D12

Truth table:

T

Qn 

(Present state)

Qn+1 

(Next state)

0

0

0

0

1

1

1

0

1

1

1

0

 

Characteristic equation: Qn+1 = TQ̅­n + T̅Qn

The T flip flop may be obtained from a J-K flip flop by making both the inputs are the same i.e. J = K.

F1 U.B Madhu 27.03.20 D13

The number of flip-flops required for constructing a mod-12 counter is :

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

Answer (Detailed Solution Below)

Option 2 : 4

Sequential Circuits Question 10 Detailed Solution

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The correct answer is option 2): 4

Concept:

For a counter with ‘n’ flip flops:

  • The total number of states = 2n (0 to 2n – 1)
  • The largest number that can be stored in the counter = 2n – 1
  • To construct a counter with any MOD number, the minimum number of flip flops required must  satisfy: Modulus ≤ 2n
  • Where n is the number of flip-flops and is the minimum value satisfying the above condition.
  • Note: A MOD-N counter is also called as a divide by N counter as the input frequency is divided by the number of states of the counter.

Calculation:

Number no. of flip – flops are required to construct mod-12 counter,

must satisfy: 2n ≥ 12 The minimum value of n satisfying the above is: n = 4

A basic memory storage element in a digital system is:

  1. Flip flop
  2. Counter
  3. Multiplexer
  4. Encoder

Answer (Detailed Solution Below)

Option 1 : Flip flop

Sequential Circuits Question 11 Detailed Solution

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  • Latches and flip-flops are the basic elements for storing information. They are made of logic gates.
  • One latch or flip-flop can store a 1-bit of information.
  • For latches, its input can affect the output as long as the enable signal is asserted (high).
  • For flip-flop, its input can affect the output only when the enable signal changes (falling edge or rising edge).

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The difference between latches and flip flops is shown

Latches

Flip Flops

Latches are building block of sequential circuits and they are built using logic gates

Flip flops are also building blocks of sequential circuits but they are made using latches

Latches continuously change the input and output changes correspondingly

Flip flop output changes only when the clock is applied

Latches are level sensitive

Flip flops are edge sensitive

Three T flip flops are connected to form a counter. The maximum states possible for the counter will be:

  1. 5
  2. 3
  3. 8
  4. 7

Answer (Detailed Solution Below)

Option 3 : 8

Sequential Circuits Question 12 Detailed Solution

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Concept:

For a counter with ‘n’ flip flops:

  • The total number of states = 2n (0 to 2n – 1)
  • The largest number that can be stored in the counter = 2n – 1

 

To construct a counter with any MOD number, the minimum number flip flops required must satisfy:

Modulus ≤ 2n

Where n is the number of flip-flops and is the minimum value satisfying the above condition.

Calculation:

The total number of states required when n = 3:

23  ≥  8

The states will vary from (0 to 7)

So the maximum states possible for the counter will be 8.

A __________ counter can be implemented using three flipflops.

  1. mod-6
  2. mod-11
  3. mod-9
  4. mod-13

Answer (Detailed Solution Below)

Option 1 : mod-6

Sequential Circuits Question 13 Detailed Solution

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Concept:

For a counter with ‘n’ flip flops:

  • The total number of states = 2n (0 to 2n – 1)
  • The largest number that can be stored in the counter = 2n – 1

 

To construct a counter with any MOD number, the minimum number flip flops required must satisfy:

Modulus ≤ 2n

Where n is the number of flip-flops and is the minimum value satisfying the above condition.

Calculation:

Given: 

n = 3

Modulus ≤ 2n

Modulus ≤ 23

Modulus ≤ 8

The most appropriate answer is option 1 i.e. Mod 6.

The number of unused states in a n-bit Johnson Counter is:

  1. 2n - 2n
  2. 2n - 1
  3. 2n - n
  4. 2n

Answer (Detailed Solution Below)

Option 1 : 2n - 2n

Sequential Circuits Question 14 Detailed Solution

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Johnson Counter: 

A Johnson counter is a modified ring counter, where the inverted output from the last flip flop is connected to the input to the first.

The circuit diagram for a 4-bit Johnson Counter is as shown:

D2

The MOD of the Johnson counter is 2n if n flip-flops are used.

For an n-bit counter, the total number of states possible is 2n. ∴ The number of unused states for a Johnson counter will be:

Unused = Total States possible - Mod of the counter

= 2n - 2n

Which of the following is not a sequential circuit?

  1. Flip flop
  2. Counter
  3. Shift register
  4. Multiplexer

Answer (Detailed Solution Below)

Option 4 : Multiplexer

Sequential Circuits Question 15 Detailed Solution

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The correct answer is option 4):(Multiplexer)

Concept:

  • Combinational logic is a type of digital logic that is implemented by Boolean circuits, where the output is a pure function of the present input only.
  • Sequential logic is a type of digital logic in which the output depends not only on the present input but also on the history of the output.
  • Sequential logic has memory while combinational logic does not.
  • Flip-flop, counter, and shift registers are sequential circuits whereas multiplexer, decoder, and encoder act like combinational circuits.
  •  A multiplexer also known as a data selector, is a device that selects between several analog or digital input signals and forwards the selected input to a single output line. The selection is directed by a separate set of digital inputs known as select lines.
  • The Multiplexer has shown as 

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Additional Information

  •  A flip-flop is a sequential digital electronic circuit having two stable states that can be used to store one bit of binary data. Flip-flops are the fundamental building blocks of all memory devices.
  • The counter is a sequential circuit consisting of a set of flip-flops which can go through a sequence of states. It is used to count the number of clock cycles. Since the clock pulses occur at known intervals, the counter can be used for measuring time such as period or frequency.
  • A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one location to the next.
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