Electronics (ECE) — MCQ Practice Questions & Answers

Question 1

For a 3-bit Johnson counter, the maximum count is:

Accepted Answer

Correct answer: B. 6 — Johnson counter (twisted ring counter) has 2n states for n flip-flops. For 3-bit: 2×3 = 6 states. It's more efficient than ripple counter but less than binary counter.

Answer

A. 3

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C. 7

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D. 8

Question 2

Design a 3-bit Up/Down counter. If control signal C=1 for Up and C=0 for Down, which additional gates are required in a synchronous design?

Accepted Answer

Correct answer: C. Multiplexers and additional logic — Up/Down counters require multiplexers to select between up and down count logic. Additional XOR/XNOR gates are needed to conditionally modify JK inputs based on control signal C

Answer

A. Only AND gates

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B. Only OR gates

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D. Only NAND gates

Question 3

In Hamming code for single error correction, if the total number of data bits is 16, how many parity bits are required?

Accepted Answer

Correct answer: C. 5 parity bits — For Hamming code, if 'p' is the number of parity bits, then 2^p ≥ (p + data bits). For 16 data bits: 2^p ≥ p + 16. Testing: 2^5 = 32 ≥ 5 + 16 = 21. ✓

Answer

A. 3 parity bits

Answer

B. 4 parity bits

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D. 6 parity bits

Question 4

A SRAM cell requires how many transistors for a 1-bit storage?

Accepted Answer

Correct answer: C. 6 transistors — A typical SRAM cell uses 6 transistors: 4 for the cross-coupled latch (2 NMOS + 2 PMOS) and 2 access transistors for read/write operations.

Answer

A. 2 transistors

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B. 4 transistors

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D. 8 transistors

Question 5

In pipelined architecture, what does increasing the number of pipeline stages primarily result in?

Accepted Answer

Correct answer: B. Increased instruction throughput but increased latency — More pipeline stages increase throughput (instructions per cycle) but increase latency (clock-to-output delay) due to increased stage delays.

Answer

A. Decreased power consumption

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C. Decreased memory requirements

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D. Reduced circuit complexity

Question 6

How does the Kogge-Stone adder compare to the Ripple Carry Adder in terms of propagation delay for a 32-bit addition?

Accepted Answer

Correct answer: B. Kogge-Stone has logarithmic delay O(log n) while RCA has linear O(n) delay — Kogge-Stone is a parallel prefix adder with O(log n) delay compared to Ripple Carry Adder's O(n) linear delay, making it faster for larger bit widths.

Answer

A. Kogge-Stone has higher delay due to complex interconnects

Answer

C. Both have the same propagation delay

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D. Ripple Carry Adder is faster for 32-bit operations

Question 7

In a complex digital system, what does 'Setup time' refer to?

Accepted Answer

Correct answer: B. Minimum time data must be stable before clock edge — Setup time is the minimum duration that the input data must be stable and valid before the active clock edge arrives at the flip-flop.

Answer

A. Time for circuit initialization

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C. Time to power up the system

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D. Duration of reset pulse

Question 8

A Moore FSM differs from a Mealy FSM in which aspect?

Accepted Answer

Correct answer: B. Output depends only on current state in Moore, but on current state and inputs in Mealy — Moore FSM outputs depend only on current state, while Mealy FSM outputs depend on both current state and current inputs, allowing faster response.

Answer

A. Number of states

Answer

C. Moore uses more flip-flops

Answer

D. Mealy cannot have feedback loops

Electronics (ECE) - MCQ Practice Questions