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
- 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
Nice questions.