ALU 101 Digital Logic Gates 2 โ Questions and Answers
Question 1: What is the Boolean expression for an OR gate with inputs A and B?
- A ยท B
- A + B (Correct answer)
- A โ B
- Aฬ ยท Bฬ
Correct answer: A + B
The OR gate is represented by the '+' operator in Boolean algebra, so its expression is A + B.
Question 2: Which of the following gates produces a HIGH output only when all inputs are LOW?
- AND
- OR
- NOR (Correct answer)
- XNOR
Correct answer: NOR
A NOR gate outputs HIGH only when all inputs are LOW, as it is the complement of the OR gate.
Question 3: An XNOR gate outputs 1 when its inputs are:
- Different
- Both 0 only
- Both 1 only
- Identical (Correct answer)
Correct answer: Identical
An XNOR (exclusive NOR) gate outputs 1 when both inputs are the same (both 0 or both 1).
Question 4: In a truth table, how many rows represent all possible inputs for a 2-input gate?
- 2
- 4 (Correct answer)
- 8
- 16
Correct answer: 4
A 2-input gate has 2ยฒ = 4 possible input combinations (00, 01, 10, 11).
Question 5: Which gate can implement addition without carry at the bit level?
- AND
- OR
- XOR (Correct answer)
- NAND
Correct answer: XOR
An XOR gate computes the sum bit of two binary inputs without considering the carry.
Question 6: What does a logic gate with a bubble on its output symbol indicate?
- Active-low output (Correct answer)
- High-impedance state
- Tri-state output
- Open-collector output
Correct answer: Active-low output
A bubble (small circle) on a gate's output symbol indicates that the output is inverted (active-low).
ALU 101 Digital Logic Gates 2
What is the Boolean expression for an OR gate with inputs A and B?