ISCET Digital Electronics Principles 2 — Questions and Answers
Question 1: What is the output of a NAND gate when both inputs are HIGH?
- LOW (Correct answer)
- HIGH
- Undefined
- Tri-state
Correct answer: LOW
A NAND gate outputs LOW only when all inputs are HIGH, making it the complement of an AND gate.
Question 2: Which number system uses base 16 with digits 0–9 and letters A–F?
- Octal
- Binary
- Hexadecimal (Correct answer)
- BCD
Correct answer: Hexadecimal
Hexadecimal (base-16) uses digits 0–9 and letters A–F to represent values 0 through 15.
Question 3: In a D flip-flop, what happens to the output Q on the active clock edge when D = 0?
- Q toggles
- Q becomes 1
- Q becomes 0 (Correct answer)
- Q retains its previous value
Correct answer: Q becomes 0
A D flip-flop transfers the D input directly to Q on the active clock edge, so Q = 0 when D = 0.
Question 4: What Boolean expression represents a 2-input XOR gate?
- A·B
- A+B
- A⊕B = A'B + AB' (Correct answer)
- A'B'
Correct answer: A⊕B = A'B + AB'
XOR (exclusive-OR) outputs HIGH when inputs differ: A'B + AB' is the canonical SOP form.
Question 5: How many bits are required to uniquely represent 32 different states?
- 4
- 5 (Correct answer)
- 6
- 8
Correct answer: 5
2⁵ = 32, so exactly 5 bits are needed to represent 32 unique states.
Question 6: Which logic family is characterized by very low power consumption and high noise immunity, making it dominant in modern ICs?
- TTL
- ECL
- CMOS (Correct answer)
- RTL
Correct answer: CMOS
CMOS draws negligible static current and offers wide noise margins, making it the standard for modern digital ICs.
Question 7: What is the decimal equivalent of the binary number 1011₂?
- 9
- 10
- 11 (Correct answer)
- 13
Correct answer: 11
1011₂ = 1×8 + 0×4 + 1×2 + 1×1 = 8+2+1 = 11₁₀.
ISCET Digital Electronics Principles 2
What is the output of a NAND gate when both inputs are HIGH?