301. In Boolean algebra, A(A’ + B) =
A) A + B
B) AB
C) B
D) A’B
Answer: B
Explanation: Expand → AA’ + AB = 0 + AB = AB.
302. The output of OR gate is 1 when
A) All inputs are 0
B) Any input is 1
C) All inputs are 1
D) None
Answer: B
Explanation: OR gives high output if any input = 1.
303. In a 4-bit binary adder, maximum output sum =
A) 1110
B) 1111
C) 10000
D) 1000
Answer: C
Explanation: 15 + 15 = 30 = 11110 (5-bit result).
304. Which device stores one bit of data?
A) Flip-flop
B) Register
C) Counter
D) Decoder
Answer: A
Explanation: Each flip-flop can store one bit.
305. The ASCII code for capital ‘A’ =
A) 65
B) 66
C) 67
D) 68
Answer: A
Explanation: ASCII of ‘A’ = 65₁₀ = 01000001₂.
306. A logic circuit that detects a specific sequence of inputs is
A) Counter
B) Sequential circuit
C) Decoder
D) Comparator
Answer: B
Explanation: Sequential circuits detect input sequences using memory.
307. In a 2’s complement system, –8 (in 4 bits) =
A) 1000
B) 0111
C) 1111
D) 0001
Answer: A
Explanation: Range: –8 to +7 → –8 = 1000.
308. Which circuit converts binary to BCD?
A) Encoder
B) Adder
C) Decoder
D) BCD converter circuit
Answer: D
Explanation: BCD converter modifies binary weights to decimal digits.
309. The maximum number of outputs for a 6-input truth table =
A) 32
B) 64
C) 128
D) 256
Answer: B
Explanation: 2⁶ = 64 combinations.
310. A 2x4 decoder has how many inputs?
A) 1
B) 2
C) 3
D) 4
Answer: B
Explanation: “2x4” → 2 inputs, 4 outputs.
311. A half adder cannot handle
A) Carry input
B) Carry output
C) Binary input
D) Sum output
Answer: A
Explanation: Half adder has no provision for carry input.
312. The Boolean equation for OR gate =
A) A + B
B) AB
C) A’B’
D) (A + B)’
Answer: A
Explanation: OR → logical addition.
313. A multiplexer is also known as
A) Data selector
B) Data distributor
C) Encoder
D) Decoder
Answer: A
Explanation: MUX selects one of many data inputs → data selector.
314. A D latch is level-sensitive while a D flip-flop is
A) Edge-sensitive
B) Level-sensitive
C) Asynchronous
D) Combinational
Answer: A
Explanation: Flip-flop changes output on clock edge.
315. In a binary adder, carry propagation delay depends on
A) Gate delay
B) Number of bits
C) Both A & B
D) Input voltage
Answer: C
Explanation: Delay increases with number of stages (bits).
316. The function of buffer gate is
A) Invert signal
B) Amplify current
C) Store data
D) Divide frequency
Answer: B
Explanation: Buffer increases drive capability without logic change.
317. Which gate is known as universal gate?
A) OR
B) NOR
C) NAND
D) XOR
Answer: C
Explanation: NAND can realize all logic functions.
318. The main function of decoder is
A) Code generation
B) Address selection
C) Data storage
D) Signal amplification
Answer: B
Explanation: Decoder selects one output line corresponding to input address.
319. Binary addition 1011 + 1101 =
A) 10110
B) 11000
C) 10100
D) 11110
Answer: D
Explanation: 11 + 13 = 24 → 11000, correction → 24 = 11000₂ (Answer: 11000).
320. 1’s complement of 11001010 =
A) 00110101
B) 00110101
C) 00110101
D) 00110101 (flip all bits)
Answer: A
Explanation: Flip bits → 00110101.
321. The Boolean simplification of AB + A’C + BC =
A) AB + A’C
B) AC + B
C) AB + C
D) AB + A’C + BC
Answer: C
Explanation: Consensus theorem → AB + A’C + BC = AB + C.
322. The purpose of edge-triggering is to
A) Remove glitches
B) Synchronize clock transitions
C) Avoid race conditions
D) All
Answer: D
Explanation: Edge-triggering ensures predictable output change at defined clock transitions.
323. The base of binary number system =
A) 8
B) 10
C) 2
D) 16
Answer: C
Explanation: Binary → base 2.
324. Full adder can be implemented using
A) 2 XOR, 2 AND, 1 OR
B) 1 XOR, 1 AND
C) 2 NAND
D) 3 NOR
Answer: A
Explanation: Standard full adder circuit.
325. A logic family with best noise immunity:
A) TTL
B) CMOS
C) ECL
D) RTL
Answer: B
Explanation: CMOS has highest noise margins and lowest power.
326. BCD representation of 15 =
A) 0001 0101
B) 0011 0110
C) 0001 0100
D) 0001 1111
Answer: A
Explanation: 1 → 0001, 5 → 0101.
327. Which of the following is sequential?
A) Encoder
B) Decoder
C) Counter
D) Multiplexer
Answer: C
Explanation: Counter depends on past clock pulses → sequential.
328. Which gate can function as inverter by tying inputs together?
A) NAND
B) NOR
C) AND
D) OR
Answer: A
Explanation: NAND with both inputs same → (A·A)’ = A’.
329. The operation of SR flip-flop is invalid when
A) S=R=0
B) S=R=1
C) S=0, R=1
D) S=1, R=0
Answer: B
Explanation: Both high produce undefined output.
330. The purpose of pull-up resistor is
A) Keep input HIGH
B) Limit current
C) Increase fan-out
D) All
Answer: A
Explanation: Pull-up maintains logic HIGH when input floating.
331. A shift register can perform
A) Delay
B) Serial-to-parallel conversion
C) Parallel-to-serial conversion
D) All
Answer: D
Explanation: Registers can shift or convert data formats.
332. In digital ICs, the typical logic 1 voltage for TTL =
A) 0V
B) 5V
C) 3.3V
D) 2.0V
Answer: D
Explanation: Logic HIGH ≥ 2.0V in TTL.
333. NAND followed by NOT =
A) AND
B) OR
C) XOR
D) NOR
Answer: A
Explanation: (AB)’’ = AB.
334. Which circuit generates square waves?
A) Monostable
B) Astable multivibrator
C) Bistable
D) Schmitt trigger
Answer: B
Explanation: Astable has no stable state → continuous oscillation.
335. The 8-bit microprocessor has addressable memory locations =
A) 64 KB
B) 256
C) 1024
D) 4096
Answer: A
Explanation: 16-bit address → 2¹⁶ = 64K.
336. The full form of TTL =
A) Transistor-Transistor Logic
B) Transistor-Triode Logic
C) Transmission-TTL Logic
D) Transistor-Track Logic
Answer: A
Explanation: TTL uses transistors for both logic and switching.
337. In CMOS, both PMOS and NMOS are used because
A) Speed
B) Power efficiency
C) Complementary switching
D) High current
Answer: C
Explanation: Complementary arrangement reduces static power.
338. The decimal equivalent of binary 11101 =
A) 27
B) 28
C) 29
D) 30
Answer: C
Explanation: 16 + 8 + 4 + 0 + 1 = 29.
339. In DeMorgan’s theorem, (A·B)’ =
A) A’ + B’
B) A’B’
C) A + B
D) A’ + B
Answer: A
Explanation: Complement of product = sum of complements.
340. The K-map rule: adjacent cells differ by
A) 2 bits
B) 1 bit
C) 3 bits
D) 4 bits
Answer: B
Explanation: Adjacent cells = differ in only 1 variable.
341. The binary number 101101 = ___ in decimal.
A) 44
B) 45
C) 46
D) 47
Answer: B
Explanation: 32 + 8 + 4 + 1 = 45.
342. The hexadecimal ‘A3’ =
A) 161
B) 162
C) 163
D) 164
Answer: A
Explanation: A=10 → 10×16 + 3 = 163.
343. In a memory cell, “write” operation means
A) Reading data
B) Changing stored bit
C) Deleting
D) Refreshing
Answer: B
Explanation: Write replaces existing data with new.
344. The Gray code for binary 1101 =
A) 1011
B) 1001
C) 1110
D) 1100
Answer: A
Explanation: Convert via XOR method → 1011.
345. The output of OR gate with both inputs 0 =
A) 1
B) 0
C) Undefined
D) High impedance
Answer: B
Explanation: OR outputs 0 if all inputs 0.
346. The output of NAND gate with both inputs 1 =
A) 0
B) 1
C) Undefined
D) Depends
Answer: A
Explanation: (1·1)’ = 0.
347. The unit of propagation delay =
A) Seconds
B) Amperes
C) Volts
D) Bits
Answer: A
Explanation: Delay measured in seconds (ns scale).
348. Which type of memory is fastest?
A) Cache
B) Main
C) Secondary
D) Virtual
Answer: A
Explanation: Cache is high-speed, close to CPU.
349. Boolean law: A + A’B = A + B is called
A) Absorption
B) Distributive
C) Consensus
D) DeMorgan
Answer: A
Explanation: Simplifies redundant terms → absorption law.
350. The smallest addressable unit of memory =
A) Bit
B) Byte
C) Word
D) Nibble
Answer: B
Explanation: Memory is addressed bytewise (8 bits).
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