Digital Circuits Week 4 Nptel Assignment Answers
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Digital Circuits Week 4 Nptel Assignment Answers (July-Dec 2025)
Question 1. The boolean expression A̅B + AB̅ + AB is equivalent to?
a) A + B
b) A̅ . B
c) A + B̅
d) A . B
Question 2. The input to a logic gate is A = 1100 and B = 1010. What will be the output, if the logic gate is a NAND gate?
a) 1101
b) 0111
c) 0110
d) 1011
Question 3. The combinational circuit implementation of the boolean function F(A,B,C) = Σ(1,2,4,7) is:
a) (diagram option)
b) (diagram option)
c) (diagram option)
d) (diagram option)
Question 4. For the following logic diagram, which expression is true?
a) AB̅ + AB̅̅̅̅
b) A̅B̅ . AB̅̅̅̅
c) AB̅ . AB
d) (A . B)(A . B̅)
Question 5. The output of the logic gate in the figure below is:
a) 0
b) 1
c) A
d) A̅
Question 6. The number of inputs and outputs in a half adder circuit are?
a) 2 and 1
b) 4 and 2
c) 1 and 1
d) 2 and 2
Question 7. The output Y in the circuit below is always ‘1’ when:
a) Two or more of the inputs P, Q, R are ‘0’
b) Two or more of the inputs P, Q, R are ‘1’
c) Any odd number of the inputs P, Q, R is ‘0’
d) Any odd number of the inputs P, Q, R is ‘1’
Question 8. In the circuit shown in the figure, if C = 0, the expression for Y is:
a) Y = AB’ + A’B
b) Y = A + B
c) Y = A’ + B’
d) Y = AB
Question 9. In the figure shown, the output Y is required to be Y = A.B + C̅D̅. The gates G1 and G2 must be respectively:
a) NOR, OR
b) OR, NAND
c) NAND, OR
d) AND, NAND
Question 10. What is the primary cause of glitches in digital circuits?
a) Manufacturing defects in the integrated circuits.
b) Variations in gate delays due to process variations.
c) Incorrect connections in the circuit layout.
d) Inadequate power supply voltage.
Question 11. The output Y of the logic circuit given below is:
a) 1
b) 0
c) X
d) X̅
Question 12. Identify the logical operations performed by the given circuits?
a) a) AND gate, b) OR gate
b) a) NAND gate, b) OR gate
c) a) OR gate, b) AND gate
d) a) NAND gate, b) NOR gate
Question 13. The Boolean function Y = AB + CD is to be realized using only 2-input NAND gates. The minimum number of gates required is:
a) 2
b) 3
c) 4
d) 5
Question 14. Which of the following Boolean Expressions correctly represents the relation between P, Q, R, and Y?
a) Y = (P OR Q) XOR R
b) Y = (P AND Q) XOR R
c) Y = (P NOR Q) XOR R
d) Y = (P XOR Q) XOR R
Question 15. Which of the following terms refers to the maximum amount of unwanted voltage (noise) that can be present at the input of a digital logic gate without causing a change in its output logic level?
a) Noise Margin
b) Noise Immunity
c) White Noise
d) Signal-to-Noise Ratio
Digital Circuits Week 4 Nptel Assignment Answers (July-Dec 2024)
Q1.Which of the following property is WRONG?
A) A XOR 0 = A’
B) A XOR 1 = A’
C) A XOR A = 0
D) A XOR A’ = 1
Answer: A) A XOR 0 = A’
Q2. Minimum number of NAND gates are required to design a 2-input XOR gate is
A) 3
B) 4
C) 5
D) 6
Answer: B) 4
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These are Digital Circuits Week 4 Nptel Assignment Answers
Q3.Which of the following logic function is implemented by the circuit given below?
A) NAND
B) NOR
C) XOR
D) XNOR
Answer: A) NAND
Q4 How many transistors are required to design a CMOS 2-input NOR gate?
A) 2 PMOS and 1 NMOS transistors
B) 1 PMOS and 2 NMOS transistors
C) 3 PMOS transistors
D) 2 PMOS and 2 NMOS transistors
Answer: D) 2 PMOS and 2 NMOS transistors
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These are Digital Circuits Week 4 Nptel Assignment Answers
Q5.What is a hazard in digital circuits?
A) An error in the physical layout of the circuit
B) A temporary fluctuation in output due to changes in input
C) A permanent fault in the circuit
D) A delay in the clock signal
Answer: B) A temporary fluctuation in output due to changes in input
Q6 In digital circuits, what type of hazard occurs when a single input change causes multiple changes in output before settling?
A) Static-1 hazard
B) Static-0 hazard
C) Dynamic hazard
D) Glitch hazard
Answer :C) Dynamic hazard
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Q7. A static-0 hazard in a digital circuit occurs when:
A) The output should remain 0, but temporarily goes to 1
B) The output should remain 1, but temporarily goes to 0
C) The output oscillates between 0 and 1
D) The output remains at a constant 0
Answer: A) The output should remain 0, but temporarily goes to 1
Q8. Which of the following options correctly represents the SUM and CARRY outputs for a half adder?
A) SUM = A XOR B, CARRY = A.B
B) SUM = A XNOR B, CARRY = A.B
C) SUM = A XOR B, CARRY = A+B
D) SUMA.B, CARRY = A XOR B
Answer: A) SUM = A XOR B, CARRY = A.B
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Q9. What is the primary difference between a half adder and a full adder?
A) A half adder can add two bits while a full adder can add three bits including the carry.
B) A half adder can subtract two bits while a full adder can add two bits.
C) A half adder can add three bits while a full adder can add two bits including the carry.
D) A half adder can multiply two bits while a full adder can add two bits.
Answer:A) A half adder can add two bits while a full adder can add three bits including the carry.
Q10.How many half adders are required to construct a full adder?
A) 1
B) 2
C) 3
D) 4
Answer:B) 2
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Q11.When the set of input data to an even parity generator is 01111, the output will be
A) 1
B) 0
C) Don’t care
D) Depends on the previous input
Answer : B) 0
Q12.Consider the circuit shown below. Which of the following statements correctly describe the output X?
A) X is the generated carry-out bit
B) X is equal to logic 1 when addition is performed and X is equal to logic 0 whensubtraction is done.
C) X is equal to logic 1 if there is an overflow during either addition or subtraction.
D) X is equal to logic 0 if there is an overflow during either addition or subtraction.
Answer: B) X is equal to logic 1 when addition is performed and X is equal to logic 0 whensubtraction is done.
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Q13. The product term to be included to remove possible static hazard for the function f(Y,W,X)=WX + W’Y’ is
A) WY’
B) XY’
C) W’X’
D) XY
Answer:B) XY’
Q14. Which of the following statement if FALSE?
A) Parity checking circuits are used for error dectection and correction
B) Parity generator circuit generates the parity bit before transmitting.
C) Parity checker circuits checks the parity at the reciever
D) Even parity checker output logic 1 when input contains even number of logic 1s
Answer: D) Even parity checker output logic 1 when input contains even number of logic 1s
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Q15.How many minimum number of transistors required to design a CMOS inverter?
A) 1 PMOS and 1 NMOS
B) 2 PMOS and 1 NMOS
C) 2 NMOS
D) 2 PMOS
Answer: A) 1 PMOS and 1 NMOS
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