# 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, Engineering MCQ, Multiple Choice Question based on Engineering, Digital Electronics MCQ, AND Gate MCQ, OR Gate MCQ, NAND Gate MCQ, Objective Questions on Logic Gate

### MULTIPLE CHOICE QUESTIONS

Q.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

Q.2. NAND gate is

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

Q.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

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

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

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

• AND
• NAND
• OR
• NOT

Q.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: $X=\bar{A+B}$

Q.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

Q.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

Q.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

Q.10. Which of the following gates are interchangeable?

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

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

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

Q.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

Q.13. The Boolean expression for XNOR is given as

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

Answer: $A \oplus B$

Q.14. A Combinational circuit can be designed using only

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

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

• 2
• 3
• 4
• 5

Q.16. A combinational circuit can be designed using only

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

Q.17. A combinational circuit can be designed using only

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

Q.18. What is the logic which controls a stair case light associated with two switches A and B located at the bottom and top of the stair case respectively?

• OR
• AND
• X-OR
• X-NOR

Q.19. The NAND gate can function as a NOT gate if

• all inputs are connected together
• inputs are left open
• one input is set to 0
• one input is Set to 1

Answer: all inputs are connected together

Q.20. The NOR gate cal, function as a NOT gate if

• all inputs are connected together
• inputs are left open
• one input is set to 0
• one input is set to 1

Answer: all inputs are connected together

Q.21. An X-OR gate gives a high output

• if there are odd number of 1 s
• if it has even number of 0s
• if the decimal value of digital word even
• for odd decimal value

Answer: if there are odd number of 1 s

Q.22. An exclusive NOR gate is logically equivalent to

• inverter followed by an X-OR gate
• X-OR gate followed by an inverter
• complement of a NOR gate
• NOT gate followed by a NOR gate

Answer: X-OR gate followed by an inverter

Q.23. The X-OR and X-NOR gates can have how many inputs?

• 2
• 1
• 4
• any number

Q.24. The logic expression $AB+\bar{A}\bar{B}$ can be implemented by giving the inputs A and B to a two-input.

• NOR gate
• NAND gate
• X-OR gate
• X-NOR gate

Q.25. The logic expression $A\bar{B}+\bar{A}B$ can be implemented by giving inputs A and B to a two-input.

• NOR gate
• NAND gate
• X-OR gate
• X-NOR gate

Q.26. Which of the following is known as a mod-2 adder?

• X-OR gate
• X-NOR gate
• NAND gate
• NOR gate

Q.27. What is the minimum number of two-input NAND gates used to perform the function of 2-input OR gate?

• One
• Two
• Three
• Four

Q.28. NOT gates are to be added to the inputs of which gate to convert it to a NAND gate?

• OR
• AND
• NOT
• X-OR

Q.29. NOT gates are to be added to the inputs of which gate to convert it to a NOR gate?

• OR
• AND
• NAND
• X-NOR