Objective Questions on Logic Gate

Objective Questions on Logic Gate

Objective Questions on Logic Gate, digital logic gate questions, MCQ on logic gate, digital logic design multiple-choice questions

MULTIPLE CHOICE QUESTIONS

1. If A, B and C are the inputs of AND gate, then the output Y is HIGH for

• A = 1, B = 1, C = 0
• A = 0, B = 0, C = 0
• A = 1, B = 1, C = 1
• A = 1, B = 0, C = 1

Answer: A = 1, B = 1, C = 1

2. NAND gate is

• AND followed by NOT
• NOT followed by AND
• Two AND gates interconnected
• OR followed by AND

Answer: AND followed by NOT

3. If one of the inputs of the 2-input logic gate is LOW, then which of the following gate still has a HIGH output is HIGH?

• AND
• NAND
• NOR
• OR

Answer: NAND

4. The Boolean expression for a 3-input AND gate is

• Y = AB + BC + CA
• Y = ABC
• Y = A + B + C
• Y = AB + C

Answer: Y = ABC

5. Which of the following logical operations has ‘+’ as its symbol?

• AND
• NAND
• OR
• NOT

Answer: OR

6. The logic expression for a NOR gate is given as

• X=\bar{A}+B
• X=A+\bar{B}
• X=A+B
• X=\bar{A+B}

Answer: X=\bar{A+B}

7. The Boolean expression for the output of a NOR gate is similar to a

• NAND gate followed by an inverter
• OR gate followed by an inverter
• AND gate followed by an inverter
• NOR gate followed by an inverter

Answer: OR gate followed by an inverter

8. A NOT gate has a HIGH output when

• The input is LOW
• The input is HIGH
• Power supply is ON
• Power supply is OFF

Answer: The input is LOW

9. An exclusive-OR gate has a HIGH output when

• All inputs are LOW
• All inputs are HIGH
• The inputs have opposite logic
• None of the above

Answer: The inputs have opposite logic

10. Which of the following gates are interchangeable?

• NAND and NOR
• NOR and OR
• AND and OR
• NOR and bubbled OR

Answer: NAND and NOR

11. A 2-input NOR gate is equivalent to a

• Negative-OR gate
• Negative-AND gate
• Negative-NAND gate
• None of the above

Answer: Negative-AND gate

12. The output ‘Y’ of the given logic diagram is

• Y = (A + B) C
• Y = AB + C
• Y = A + B + C
• Y = A + BC

Answer: Y = (A + B) C

13. The Boolean expression for XNOR is given as

• A+B
• A.B
• A \oplus B
• \bar{A \oplus B}

Answer: A \oplus B

14. A Combinational circuit can be designed using only

• AND gates
• OR gates
• OR and X-NOR gates
• NOR gates

Answer: NOR gates

15. How many NOR gates are required to obtain AND operations?

• 2
• 3
• 4
• 5

Answer: 3