351. Which flip-flop is used for frequency division?
A) SR flip-flop
B) JK flip-flop
C) D flip-flop
D) T flip-flop
Answer: D
Explanation: T flip-flop toggles output on each clock → divides frequency by 2.
352. The function of a counter is to
A) Add numbers
B) Generate clock
C) Count pulses
D) Shift data
Answer: C
Explanation: Counters increment or decrement on clock pulses.
353. The number of flip-flops needed for a MOD-16 counter =
A) 2
B) 3
C) 4
D) 5
Answer: C
Explanation: 2⁴ = 16 → requires 4 flip-flops.
354. A ring counter with 4 flip-flops has how many states?
A) 4
B) 8
C) 16
D) 2⁴
Answer: A
Explanation: Ring counter = n states for n flip-flops.
355. The number 11111111₂ =
A) 128
B) 255
C) 256
D) 512
Answer: B
Explanation: 2⁸ – 1 = 255.
356. Which flip-flop is most versatile?
A) SR
B) D
C) JK
D) T
Answer: C
Explanation: JK can perform all flip-flop operations by input selection.
357. The output of XOR gate is 1 when
A) Inputs are equal
B) Inputs are different
C) One input is 0
D) Both 0
Answer: B
Explanation: XOR → “exclusive OR” = 1 if inputs differ.
358. The Boolean expression A + A’B simplifies to
A) A + B
B) B
C) A
D) AB
Answer: A
Explanation: Absorption law → A + A’B = A + B.
359. A 3-bit binary up-counter counts from
A) 0–7
B) 1–7
C) 0–8
D) 1–8
Answer: A
Explanation: 3 bits → 2³ = 8 states → 0 to 7.
360. The output of 3-input AND gate is 1 for
A) Any input = 1
B) All inputs = 1
C) All inputs = 0
D) Alternate inputs
Answer: B
Explanation: AND gate output is 1 only when all inputs = 1.
361. A 4-bit shift register can store
A) 1 bit
B) 2 bits
C) 4 bits
D) 8 bits
Answer: C
Explanation: Each flip-flop stores one bit → 4 FFs = 4 bits.
362. The K-map is a tool for
A) Simplifying Boolean expressions
B) Generating waveforms
C) Counting pulses
D) Converting codes
Answer: A
Explanation: Karnaugh map simplifies Boolean logic visually.
363. A 1-to-8 demultiplexer has ___ select lines.
A) 1
B) 2
C) 3
D) 8
Answer: C
Explanation: 2ⁿ = 8 → n = 3 select lines.
364. The main drawback of dynamic RAM compared to static RAM is
A) Speed
B) Cost
C) Size
D) Power
Answer: A
Explanation: DRAM slower due to refresh cycles.
365. Which device is used as a memory element in computers?
A) Diode
B) Transistor
C) Flip-flop
D) Resistor
Answer: C
Explanation: Flip-flops store one bit each.
366. The 2’s complement of 0101 =
A) 1011
B) 1010
C) 0110
D) 1001
Answer: B
Explanation: 0101 → 1’s complement 1010 → +1 = 1011.
367. The propagation delay in digital circuits affects
A) Accuracy
B) Speed
C) Frequency
D) All
Answer: D
Explanation: Delay limits max frequency & causes timing errors.
368. A sequential circuit differs from combinational because
A) It has feedback
B) It is faster
C) It is linear
D) It has no output
Answer: A
Explanation: Sequential circuits have feedback for memory.
369. In a JK flip-flop, race-around occurs when
A) J = K = 1
B) J = 0, K = 0
C) J = 1, K = 0
D) Clock is LOW
Answer: A
Explanation: With J=K=1, output toggles rapidly → race condition.
370. To avoid race-around, we use
A) Master-slave JK
B) D flip-flop
C) Edge-trigger
D) All
Answer: D
Explanation: These methods control timing to eliminate racing.
371. A multiplexer selects
A) One output from many inputs
B) One input from many outputs
C) Many outputs from one input
D) None
Answer: A
Explanation: MUX = data selector → 1 output from many inputs.
372. A decoder converts
A) Binary to decimal
B) Decimal to binary
C) Binary to analog
D) Analog to digital
Answer: A
Explanation: Decoder activates 1 of 2ⁿ outputs for given input.
373. A 4-bit synchronous counter uses
A) Common clock
B) Independent clocks
C) Analog clock
D) Asynchronous delay
Answer: A
Explanation: Synchronous → all flip-flops driven by same clock.
374. A flip-flop is a
A) Combinational circuit
B) Sequential circuit
C) Arithmetic circuit
D) Memoryless system
Answer: B
Explanation: Flip-flop stores previous state → sequential.
375. A binary 0101 represents decimal
A) 4
B) 5
C) 6
D) 7
Answer: B
Explanation: (0101)₂ = 5₁₀.
376. The number of possible combinations with n binary bits =
A) n
B) 2ⁿ
C) n²
D) 2ⁿ⁻¹
Answer: B
Explanation: Each bit 0/1 → total = 2ⁿ.
377. The smallest unit of data representation =
A) Byte
B) Word
C) Bit
D) Nibble
Answer: C
Explanation: Bit = binary digit (0 or 1).
378. A 2-input XOR gate output = 1 for
A) 00
B) 11
C) 01 or 10
D) 10 only
Answer: C
Explanation: XOR outputs 1 for unequal inputs.
379. Decimal 25 = ___ in binary.
A) 11000
B) 11001
C) 11010
D) 11100
Answer: B
Explanation: 25₁₀ = 11001₂.
380. The 8-bit register can store ___ different combinations.
A) 8
B) 16
C) 128
D) 256
Answer: D
Explanation: 2⁸ = 256 combinations.
381. The full form of EPROM =
A) Erasable Programmable Read-Only Memory
B) Electrical Programmable ROM
C) Enhanced Programmable ROM
D) None
Answer: A
Explanation: EPROM erasable by UV light.
382. ROM stands for
A) Random Operating Memory
B) Read Only Memory
C) Read Output Memory
D) Random Output Memory
Answer: B
Explanation: ROM → pre-programmed permanent memory.
383. The process of converting analog to digital =
A) Sampling
B) Quantization
C) ADC
D) DAC
Answer: C
Explanation: ADC = Analog-to-Digital Converter.
384. Which gate has output low only when all inputs high?
A) AND
B) NOR
C) NAND
D) XOR
Answer: C
Explanation: NAND = inverse of AND.
385. In binary subtraction, 1 – 1 =
A) 0
B) 1
C) –1
D) Borrow
Answer: A
Explanation: 1 – 1 = 0, no borrow.
386. The complement of A + BC is
A) A’B’C’
B) A’B’ + C’
C) A’B’ + C
D) A’(B’ + C’)
Answer: D
Explanation: (A + BC)’ = A’(B’ + C’).
387. Logic level ‘1’ in positive logic means
A) Low voltage
B) High voltage
C) Negative potential
D) None
Answer: B
Explanation: In positive logic, 1 = high voltage.
388. The delay in propagation from input to output =
A) Gate delay
B) Setup time
C) Hold time
D) Clock skew
Answer: A
Explanation: Gate delay = time for output to respond.
389. The Boolean expression for a 2-input NAND gate =
A) AB
B) (A + B)’
C) (AB)’
D) (A’ + B)
Answer: C
Explanation: NAND = complement of AND.
390. BCD code can represent up to
A) 9
B) 15
C) 10
D) 16
Answer: A
Explanation: BCD uses 4 bits for 0–9.
391. Which of these is non-volatile memory?
A) SRAM
B) DRAM
C) ROM
D) Cache
Answer: C
Explanation: ROM retains data without power.
392. The term fan-out refers to
A) No. of inputs
B) No. of gates driven by output
C) No. of outputs
D) Power consumption
Answer: B
Explanation: Fan-out = output driving capacity.
393. The Boolean function (A + B)(A + B’) simplifies to
A) A
B) B
C) AB
D) A + B
Answer: A
Explanation: (A + B)(A + B’) = A + BB’ = A.
394. Binary 100110 = decimal
A) 36
B) 38
C) 39
D) 44
Answer: B
Explanation: 32 + 4 + 2 = 38.
395. A half subtractor has ___ inputs and ___ outputs.
A) 2, 1
B) 2, 2
C) 1, 2
D) 3, 2
Answer: B
Explanation: Inputs: A, B; Outputs: Difference, Borrow.
396. The logic expression for half subtractor difference =
A) A + B
B) A ⊕ B
C) AB
D) A’B
Answer: B
Explanation: Difference = XOR of A, B.
397. The logic expression for half subtractor borrow =
A) A’B
B) AB’
C) AB
D) A + B’
Answer: A
Explanation: Borrow when A=0, B=1 → A’B.
398. A full subtractor requires how many inputs?
A) 2
B) 3
C) 4
D) 1
Answer: B
Explanation: Inputs: A, B, Borrow_in.
399. The decimal 50 = ___ in hexadecimal.
A) 28
B) 31
C) 32
D) 2F
Answer: D
Explanation: 50₁₀ ÷ 16 = 3 remainder 2 → 32₁₆.
400. The logic family with the fastest speed is
A) TTL
B) CMOS
C) ECL
D) RTL
Answer: C
Explanation: Emitter Coupled Logic (ECL) offers highest speed.
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