49+ Critical Digital Electronics MCQs and Answers for Competitive exams

Digital Electronics MCQ
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Digital Electronics MCQ

1. What is the number of outputs of a full adder circuit?

1) Two

2) Three

3) Four

4) One

Solution: 2) Three

How a full adder works? Check Here!

2. What is the expression for the sum(s) of a half adder if the inputs are A & B?

1) S = A OR B

2) S = A AND B

3) S = A XNOR B

4) S = A XOR B

Solution: 4) A XOR B

3. What is the sum(S) expression of a full adder if the inputs are A, B & C?

1) S = A OR B AND C

2) S = A AND B OR C

3) S = A XNOR B XOR C

4) S = A XOR B XOR C

Solution: 4) A XOR B XOR C

4. What is the result of the binary sum?

 10101 + 1011

Do you know how to perform binary addition in digital electronics? Click to know!

1) 1 0 0 0 0

2) 1 0 1 0 1 0

3) 1 0 0 0 0 0

4) 1 1 1 1 0 0

Solution: 3) 1 0 0 0 0 0

5. Which of these following logic gates gives a high output when both the inputs are low?

1) NOR gate

2) NOT gate

3) NAND gate

4) ALL OF THE ABOVE

Solution: 4) ALL OF THE ABOVE

6. Which of these following does not include in an ALU (Arithmetic Logic Unit)?

1) Adder

2) Subtractor

3) Multiplexer

4) None of the above

Solution: 3) Multiplexer

How a multiplexer works? Find out in detail!

7. which logic gate itself is a combinational circuit?

1) XOR

2) NAND

3) NOR

4) NOT

Solution: 1) XOR

8. How many bits does the sum of the full adder consists of?

1) Four bits

2) Three bits

3) Two bits

4) Five bits

Solution: 3) Two bits

9. A combinational circuit calculates the arithmetic sum in a parallel way. What is the name of the adder?

1) Sequential Adder

2) Parallel Adder

3) Serial Adder

4) Both 1) & 2)

Solution: 2) Parallel Adder

10. What is the primary object that is needed for VLSI technology?

1)  NOR gate

2) NAND gate

3) Both 1) and 2)

4) Gate array

Solution: 4) Gate array.

11. Choose whether the below-given statement is true or false.

Statement: A binary subtractor can be made using a binary adder.

  1. True
  2. False

Solution: (1). True

How binary adders can make binary subtractors! Click to know!

12. A circuit takes single input but provides multiple outputs. Identify which circuit it could be.

1) Multiplexer

2) Demultiplexer

3) Encoder

4) All of them

Solution: 2) Demultiplexer

13. What does a multiplexer do?

1) It takes multiple inputs and provides a single output.

2) It takes a single output and offers multiple outputs.

3) It inverts the input.

4) None of the above.

Solution: 1) It takes multiple inputs and provides a single output.

14. A half subtractor provides how many outputs?

1) One

2) Four

3) Three

4) Two

Solution: 4) Two

15. Mark the given statement as True or false.

Statement: An Encoder can be used as a transducer. 

  1. True
  2. False

Solution: (1). True

16. How does a priority set?

1) The lower the subscript number, the higher the priority.

2) The higher the subscript number, the lower the priority.

3) The higher the subscript number, the higher the priority.

4) None of the above.

Solution: 3) The higher the subscript number, the higher the priority.

17. Find out the result of the BCD addition.

0110 + 0101

1) 10001

2) 11001

3) 1011

4) 1111

Solution: 1) 10001

What is BCD Adder? Know Here!

18. Find out the result of the binary subtraction?

1101 – 1011

Do you know how to perform binary subtraction in digital electronics? Click to know!

1) 10001

2) 0010

3) 1011

4) 0001

Solution: 2) 0010

19. Mark the given statement as True or false.

Statement: The logical expression for both the full adders and full subtractors are the same.

  1. True
  2. False

Solution: (1). True

20. Which type of complement method is used for the decimal number system?

1) 10’s compliment

2) 8’s compliment

3) 9’s compliment

4) Both 1) and 3)

Solution: 4) Both 1) and 3)

21. How many select lines will be there if the inputs of a MUX are 8?

1) One

2) Four

3) Three

4) Five

Solution: 3) Three

22. How many select lines will be there if the inputs of a DEMUX are 4?

1) One

2) Five

3) Three

4) Two

Solution: 1) Two

23. Recording a video clip is which type of operation?

1) Multiplexing

2) De Multiplexing

3) Encoding

4) Decoding

Solution: 3) Encoding

24. A half binary adder is implemented using basic gates. How many and gates will be required?

1) One

2) Two

3) Three

4) Four

Solution: 1) One

25. Mark the given statement as True or false.

Statement: Multiplexers cannot implement Boolean functions.

  1. True
  2. False

Solution: (2). False

26. Which circuit can perform the increment operation of an ALU?

1) Adder

2) Subtractor

3) Both 1) and 2)

4) None of them

Solution: 3) Both 1) and 2)

27. Mark the given statement as True or false.

Statement: Technologies like TDM, FDM, CDMA, etc., uses multiplexers and demultiplexers.  

  1. True
  2. False

Solution: (1). True

28. A decoder has an output of 2n. How many inputs does it consume?

1) n

2) 2n

3) 2n – 1

4) n-1

Solution: 1) n

29. Which type of basic gates is most necessary for Encoders?

1) OR gates

2) AND gates

3) NOT gates

4) All of the above

Solution: 1) OR gates

30. Mark the given statement as True or false.

Statement: DTMF is Diode Time Multiplexer Frequency. 

  1. True
  2. False

Solution: (2). False. DTMF – DUAL TONE MULTIPLE FREQUENCY.

31. What is the lowest number of NAND gates required for a half subtractors?

1) Four

2) Five

3) Six

4) Seven

Solution: 2) Five

32. A decoder has four input lines. How many output lines will be there?

1) Eight

2) One

3) Four

4) Sixteen

Solution: 4) Sixteen

33. Mark the given statement as True or false.

Statement: An encoder takes multiple data inputs and converts them into a single output with select lines. 

  1. True
  2. False

Solution: (2). False

34. What is min-term?

1) Product of sum

2) Sum of product

3) Product of product

4) Sum of the sum

Solution: 1) Product of sum

35. Find the application of a MUX.

1) It is used in Analog to Digital converters and Digital to analog converters in digital electronics.

2) It is used in rectifiers.

3) It is used in filters.

4) None of the above is correct.

Solution: 1) It is used in Analog to Digital converters and Digital to analog converters in digital electronics.

36. Mark the given statement as True or false.

Statement: An operation in Flip Flop is faster than an operation in the multiplexer.

  1. True
  2. False

Solution: (2). False

37. Which IC works as a multiplexer?

1) 74HA198

2) 74HC150

3) 74CH199

4) 74HC157

Solution: 4) 74HC157

38. Which IC works as a demultiplexer?

1) 74HC83

2) 74HC38

3) 74CH19

4) 74HC15

Solution: 1) 74HC83

39. Which IC works as Encoder?

1) HT85A

2) HT87B

3) HT12E

4) HT74F

Solution: 3) HT12E

40. What is the lowest no. of OR gate required for the given expression?

Y = A’B + B’A

1) 1

2) 2

3) 4

4) 5

Solution: 1) 1

41. What is the lowest no. of AND gate required for the given expression?

Y = A’B + B’A

1) 1

2) 2

3) 4

4) 5

Solution: 2) 2

42. What is the lowest no. of NAND gates required to make an inverter?

1) 1

2) 2

3) 3

4) 4

Solution: 1) 1

43. What is the lowest no. of NOR gates required to make an OR gate?

1) 1

2) 2

3) 3

4) 4

Solution: 2) 2

44. Which gates are known as universal gates in digital electronics ?

1) OR and AND

2) NOT and XOR

3) NOR and NAND

4) All of them

Solution: 3) NOR and NAND

45. A truth table is given below where A and B are the provided inputs, and from Y the output is taken. Identify the Logic gate.

Digital Electronics MCQ Table – 1

1) XOR

2) NAND

3) XNOR

4) NOR

Solution: 3) XNOR

46. A truth table is given below where A and B are the provided inputs, and from Y the output is taken, for a digital electronics circuitry. Identify the Logic gate.

Digital Electronics MCQ Table – 2

1) XOR

2) NAND

3) XNOR

4) NOR

Solution: 4) NOR

47. Find the odd one out from the digital electronics circuitry.

1) MULTIPLEXER

2) FLIP/FLOPS

3) REGISTERS

4) COUNTERS

Solution: 1) MULTIPLEXER

48. What is the lowest no. of NOT gate required for the given expression?

Y = A’B + B’C + AC

1) 1

2) 2

3) 3

4) 4

Solution: 1) 1

49. Find the odd one out.

1) DEMULTIPLEXERS

2) ENCODERS

3) HALF ADDERS

4) FULL SUBTRACTORS

Solution: 1) DEMULTIPLEXERS

50. A truth table is given below where A and B are the provided inputs, and from Y the output is taken, for a digital electronics circuitry. Identify the combinational circuit.

ABY
LOWLOWLOW
LOWHIGHHIGH
HIGHLOWHIGH
LOWLOWLOW
Digital Electronics MCQ Table – 3

1) SUBTRACTOR

2) MULTIPLEXER

3) ADDER

4) Both 1) and 3)

Solution: 4) Both 1) and 3)

Digital Electronics MCQ
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