151. The decimal equivalent of binary number 11011 is
A) 25
B) 27
C) 29
D) 31
Answer: B
Explanation: 11011₂ = 16 + 8 + 0 + 2 + 1 = 27₁₀.
152. Which of the following is a universal gate?
A) AND
B) OR
C) NAND
D) EX-OR
Answer: C
Explanation: NAND can realize any Boolean function → universal gate.
153. The output of an AND gate with inputs A = 1 and B = 0 is
A) 0
B) 1
C) Undefined
D) High impedance
Answer: A
Explanation: AND = A·B → 1×0 = 0.
154. In Boolean algebra, A + A’B = ?
A) A + B
B) A + B’
C) A + AB’
D) A + 0
Answer: A
Explanation: Simplifies to A + B (using Absorption law).
155. Which gate is equivalent to a negative OR gate?
A) AND
B) NOR
C) NAND
D) XOR
Answer: B
Explanation: Negative OR = NOR gate = (A + B)’.
156. A 3-input AND gate will have how many input combinations?
A) 4
B) 6
C) 8
D) 10
Answer: C
Explanation: For n inputs → 2ⁿ combinations = 8.
157. The minimum number of NAND gates required to implement an OR gate is
A) 1
B) 2
C) 3
D) 4
Answer: C
Explanation: OR = (A’B’)’ → requires 3 NANDs.
158. What is the output of an OR gate when both inputs are 0?
A) 0
B) 1
C) High
D) Indeterminate
Answer: A
Explanation: OR gives 1 if any input = 1 → both 0 → output = 0.
159. The expression A’B + AB’ is called
A) Exclusive NOR
B) Exclusive OR
C) NAND
D) NOR
Answer: B
Explanation: A’B + AB’ = XOR operation.
160. The operation performed by a NOT gate is called
A) ANDing
B) ORing
C) Inversion
D) Addition
Answer: C
Explanation: NOT gate inverts input logic → output = complement.
161. Which circuit converts analog to digital?
A) DAC
B) ADC
C) Amplifier
D) Oscillator
Answer: B
Explanation: ADC (Analog to Digital Converter) converts analog signals to digital form.
162. Which of the following flip-flops does not have a “toggle” mode?
A) T flip-flop
B) JK flip-flop
C) D flip-flop
D) SR flip-flop
Answer: C
Explanation: D flip-flop only stores data, no toggle function.
163. The main drawback of asynchronous counters is
A) High speed
B) Cumulative delay
C) Complexity
D) Power dissipation
Answer: B
Explanation: Ripple effect causes cumulative propagation delay.
164. In synchronous counters, all flip-flops are triggered by
A) Different clocks
B) Same clock
C) No clock
D) Random pulses
Answer: B
Explanation: Common clock edge synchronizes all flip-flops.
165. Which of the following codes is self-complementary?
A) Gray
B) BCD
C) Excess-3
D) ASCII
Answer: C
Explanation: Excess-3 is self-complementary — complement by bit inversion.
166. In a 4-bit binary counter, after 1111, the next state is
A) 0000
B) 1110
C) 1000
D) 1010
Answer: A
Explanation: 1111 + 1 → carry resets → 0000.
167. What is the decimal equivalent of hexadecimal 2F?
A) 47
B) 37
C) 42
D) 27
Answer: A
Explanation: 2F₁₆ = (2×16) + 15 = 47₁₀.
168. The most significant bit (MSB) in a signed binary number indicates
A) Magnitude
B) Sign
C) Overflow
D) Parity
Answer: B
Explanation: MSB = 0 for positive, 1 for negative (sign bit).
169. The circuit that detects a specific binary number is called
A) Comparator
B) Decoder
C) Encoder
D) Multiplexer
Answer: B
Explanation: Decoder activates output for a specific binary input.
170. Which of the following is a combinational circuit?
A) Counter
B) Flip-flop
C) Multiplexer
D) Register
Answer: C
Explanation: Multiplexer output depends only on present input combination.
171. The 1’s complement of binary 0101 is
A) 1010
B) 0101
C) 1111
D) 1001
Answer: A
Explanation: 1’s complement = invert all bits → 0101 → 1010.
172. The main difference between SRAM and DRAM is
A) Storage mechanism
B) Access time
C) Refresh requirement
D) All of the above
Answer: D
Explanation: SRAM = flip-flops; DRAM = capacitors needing refresh.
173. A ring counter with 4 flip-flops will have how many states?
A) 2⁴ = 16
B) 4
C) 8
D) 5
Answer: B
Explanation: Ring counter cycles through n states (number of FFs).
174. The binary code for decimal number 10 in BCD is
A) 1010
B) 0001 0000
C) 0001 0001
D) 0000 1010
Answer: B
Explanation: BCD = 0001 (1) + 0000 (0) = 0001 0000.
175. What does the term “fan-out” refer to?
A) Speed of logic gate
B) Power consumption
C) Number of inputs a gate can drive
D) Noise immunity
Answer: C
Explanation: Fan-out = number of similar inputs driven by one gate output.
176. Which flip-flop can be converted into a T flip-flop by feedback?
A) JK
B) D
C) SR
D) None
Answer: B
Explanation: D FF → connect Q’ to D → acts as T flip-flop.
177. The primary advantage of CMOS logic is
A) Low speed
B) Low power consumption
C) High cost
D) Complex circuit
Answer: B
Explanation: CMOS uses complementary transistors → minimal static power.
178. The input code 1000 to a 3-to-8 decoder is
A) Invalid
B) Output Y0 high
C) Output Y4 high
D) Output Y8 high
Answer: A
Explanation: 3 inputs → only 0–7 valid codes → 1000 invalid.
179. Which of the following is not a sequential circuit?
A) Counter
B) Register
C) Multiplexer
D) Shift register
Answer: C
Explanation: Multiplexer is purely combinational.
180. A full adder can be built using how many half adders?
A) 1
B) 2
C) 3
D) 4
Answer: B
Explanation: Full adder = 2 half adders + OR gate for carry.
181. The basic memory element in digital systems is
A) Multiplexer
B) Flip-flop
C) Decoder
D) Register
Answer: B
Explanation: Flip-flops store 1 bit each — building block of memory.
182. How many select lines are required for a 32:1 multiplexer?
A) 4
B) 5
C) 6
D) 8
Answer: B
Explanation: 2⁵ = 32 → 5 select lines.
183. The binary number 101011 represents what decimal number?
A) 43
B) 45
C) 47
D) 55
Answer: A
Explanation: 32 + 8 + 2 + 1 = 43.
184. The logic gate equivalent to (A + B)’(A + C)’ is
A) NOR
B) NAND
C) AND
D) OR
Answer: C
Explanation: Using De Morgan’s → (A + B)’(A + C)’ = A’B’C’ → AND equivalent.
185. The term “setup time” in flip-flops refers to
A) Minimum time input must be stable before clock edge
B) Time for output to stabilize
C) Time to store data
D) None
Answer: A
Explanation: Setup time = stable input period before clock transition.
186. What is the maximum number of outputs for a 4-line decoder?
A) 8
B) 12
C) 16
D) 32
Answer: C
Explanation: Decoder: 2ⁿ outputs → 2⁴ = 16.
187. In Gray code, successive numbers differ by
A) 1 bit
B) 2 bits
C) 3 bits
D) 4 bits
Answer: A
Explanation: Gray code ensures only 1 bit changes between successive codes.
188. The device used to select one of several input lines is
A) Decoder
B) Multiplexer
C) Encoder
D) Comparator
Answer: B
Explanation: Multiplexer (MUX) selects one input using control signals.
189. The binary equivalent of decimal 125 is
A) 1111011
B) 1111101
C) 1111100
D) 1100111
Answer: B
Explanation: 125 = 64 + 32 + 16 + 8 + 4 + 1 = 1111101₂.
190. The propagation delay is the time
A) Between input and output changes
B) Of clock pulse
C) Between voltage rise
D) Of current
Answer: A
Explanation: Time taken for output to respond after input transition.
191. Which flip-flop is known as a “toggle” flip-flop?
A) SR
B) JK
C) D
D) T
Answer: D
Explanation: T flip-flop toggles output for each clock when T=1.
192. The basic storage unit in a computer memory is
A) Bit
B) Byte
C) Word
D) Register
Answer: A
Explanation: Bit = single binary digit (0 or 1).
193. A D latch is level triggered while a D flip-flop is
A) Edge triggered
B) Level triggered
C) Asynchronous
D) Transparent
Answer: A
Explanation: D flip-flop changes output only at clock edge.
194. A 2-bit binary multiplier has how many AND gates?
A) 2
B) 3
C) 4
D) 5
Answer: C
Explanation: 2×2 multiplication → 4 ANDs for partial products.
195. Which logic gate is known as “inhibitor”?
A) AND
B) OR
C) NAND
D) NOR with one inverted input
Answer: D
Explanation: NOR gate with inverted input acts as inhibitor.
196. The output of XOR gate with three inputs A, B, C is 1 when
A) Even number of 1s
B) Odd number of 1s
C) All 1s
D) None 1
Answer: B
Explanation: XOR gives 1 for odd number of 1s.
197. Which is faster — static RAM or dynamic RAM?
A) Static
B) Dynamic
C) Both equal
D) Depends on clock
Answer: A
Explanation: SRAM (flip-flops) faster than DRAM (capacitor-based).
198. Which code does not have a unique representation of digits?
A) BCD
B) Gray
C) Binary
D) Excess-3
Answer: B
Explanation: Gray code cyclic — multiple patterns possible per number sequence.
199. The function of a demultiplexer is
A) Many-to-one
B) One-to-many
C) Many-to-many
D) None
Answer: B
Explanation: Demux routes one input to one of many outputs.
200. The decimal number 100 in binary form is
A) 1100100
B) 1001100
C) 1010000
D) 1100001
Answer: A
Explanation: 100₁₀ = 64 + 32 + 4 = 1100100₂.
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