BEE Digital Logic and Systems 2 — Questions and Answers
Question 1: Which minimization technique uses a tabular method to find the prime implicants of a Boolean function?
- Karnaugh map
- Quine-McCluskey method (Correct answer)
- De Morgan's theorem
- Shannon expansion
Correct answer: Quine-McCluskey method
The Quine-McCluskey method is a tabular algorithm for finding all prime implicants, useful for functions with many variables where K-maps become impractical.
Question 2: In a JK flip-flop, what is the output when both J=1 and K=1?
- Set (Q=1)
- Reset (Q=0)
- No change
- Toggle (Q changes state) (Correct answer)
Correct answer: Toggle (Q changes state)
When J=K=1, the JK flip-flop toggles its output on each clock edge, which eliminates the undefined state of the SR flip-flop.
Question 3: A 4-bit ripple carry adder adds two numbers in how many gate delays compared to a carry look-ahead adder?
- Fewer gate delays
- The same gate delays
- More gate delays (Correct answer)
- Exactly twice the delays
Correct answer: More gate delays
A ripple carry adder propagates carry serially through each stage, resulting in more gate delays than a carry look-ahead adder which computes carries in parallel.
Question 4: Which of the following is a universal gate?
- AND gate
- OR gate
- NAND gate (Correct answer)
- XOR gate
Correct answer: NAND gate
NAND (and NOR) gates are universal because any Boolean function can be implemented using only NAND gates.
Question 5: In a Moore machine, the output depends on:
- Current inputs only
- Current state and inputs
- Current state only (Correct answer)
- Previous state and inputs
Correct answer: Current state only
In a Moore machine, outputs are a function of the current state only, making them synchronous with the clock.
Question 6: What does a tri-state buffer output when its enable signal is inactive?
- Logic 0
- Logic 1
- High impedance (Z) (Correct answer)
- Undefined
Correct answer: High impedance (Z)
A tri-state buffer enters a high-impedance state when disabled, effectively disconnecting its output from the bus.
Question 7: How many product terms (minterms) does a 3-variable Boolean function have in total?
- 4
- 6
- 8 (Correct answer)
- 16
Correct answer: 8
A 3-variable Boolean function has 2³ = 8 possible minterms, one for each combination of input values.
BEE Digital Logic and Systems 2
Which minimization technique uses a tabular method to find the prime implicants of a Boolean function?