# Objective Questions on Logic Gate

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## 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

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

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

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

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

• AND
• NAND
• OR
• NOT

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

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

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

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

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