Q.1 What is the basic building block of digital circuits?
Transistor
Resistor
Capacitor
Inductor
Explanation - Transistors act as switches or amplifiers and are the fundamental building blocks of digital circuits.
Correct answer is: Transistor
Q.2 Which logic gate outputs HIGH only when all inputs are HIGH?
AND
OR
NAND
NOR
Explanation - An AND gate outputs HIGH (1) only when all its inputs are HIGH (1).
Correct answer is: AND
Q.3 Which logic gate gives LOW output only when all inputs are HIGH?
NAND
NOR
XOR
AND
Explanation - A NAND gate is the complement of an AND gate. It gives LOW output only when all inputs are HIGH.
Correct answer is: NAND
Q.4 What is the output of an OR gate if all inputs are LOW?
HIGH
LOW
Depends on the number of inputs
Undefined
Explanation - An OR gate outputs HIGH if at least one input is HIGH. If all inputs are LOW, the output is LOW.
Correct answer is: LOW
Q.5 Which gate is called an 'inverting gate'?
NOT
AND
OR
XOR
Explanation - A NOT gate inverts the input logic level: HIGH becomes LOW, LOW becomes HIGH.
Correct answer is: NOT
Q.6 Which of the following is a universal gate?
AND
OR
NAND
XOR
Explanation - NAND and NOR gates are universal gates because any Boolean function can be implemented using only NAND or only NOR gates.
Correct answer is: NAND
Q.7 What is the output of XOR gate when both inputs are the same?
HIGH
LOW
Depends on input
Undefined
Explanation - XOR outputs HIGH when inputs are different. If both inputs are the same, output is LOW.
Correct answer is: LOW
Q.8 Which gate is used to perform addition in digital circuits?
AND
OR
XOR
NOR
Explanation - XOR gates are used in half-adders and full-adders to perform binary addition.
Correct answer is: XOR
Q.9 What is a flip-flop used for in digital circuits?
Amplifying signals
Storing data
Generating clock signals
Filtering noise
Explanation - Flip-flops are bistable devices used to store binary information (0 or 1).
Correct answer is: Storing data
Q.10 Which flip-flop changes state on the clock edge?
SR Flip-Flop
D Flip-Flop
T Flip-Flop
JK Flip-Flop
Explanation - D Flip-Flops are edge-triggered and change state only on a specific clock edge (rising or falling).
Correct answer is: D Flip-Flop
Q.11 What is the function of a multiplexer (MUX)?
Select one input from many
Perform arithmetic operations
Store data
Invert signals
Explanation - A multiplexer selects one of many inputs and routes it to a single output line based on select lines.
Correct answer is: Select one input from many
Q.12 What does a decoder do?
Converts binary input to one of many outputs
Adds two binary numbers
Stores information
Generates clock pulses
Explanation - A decoder takes n inputs and activates one of 2^n outputs based on the input combination.
Correct answer is: Converts binary input to one of many outputs
Q.13 What is the output of a NOR gate if all inputs are LOW?
HIGH
LOW
Depends on number of inputs
Undefined
Explanation - A NOR gate is the complement of OR. If all inputs are LOW, output is HIGH.
Correct answer is: HIGH
Q.14 Which gate can be used to implement a basic memory element?
AND
OR
NOR
XOR
Explanation - SR Flip-Flop can be implemented using cross-coupled NOR gates, forming a basic memory element.
Correct answer is: NOR
Q.15 Which gate outputs HIGH only when inputs are different?
AND
OR
XOR
NAND
Explanation - XOR (Exclusive OR) outputs HIGH when inputs differ, otherwise LOW.
Correct answer is: XOR
Q.16 A combinational circuit has:
Memory
No memory
Clocked operation
Sequential operation
Explanation - Combinational circuits produce outputs only based on current inputs and have no memory.
Correct answer is: No memory
Q.17 Which circuit has outputs dependent on current input and past state?
Combinational circuit
Sequential circuit
Logic gate
Decoder
Explanation - Sequential circuits include memory elements, so outputs depend on current inputs and past states.
Correct answer is: Sequential circuit
Q.18 Which gate combination forms an SR Flip-Flop?
Two AND gates
Two OR gates
Two NOR gates
Two XOR gates
Explanation - An SR Flip-Flop can be implemented using two cross-coupled NOR gates.
Correct answer is: Two NOR gates
Q.19 What is the primary purpose of a buffer in digital circuits?
Amplify signal
Invert signal
Store data
Select inputs
Explanation - Buffers are used to strengthen the signal without inverting it.
Correct answer is: Amplify signal
Q.20 Which device converts serial data into parallel data?
Multiplexer
Demultiplexer
Shift Register
Counter
Explanation - Shift registers can convert serial input data into parallel output format.
Correct answer is: Shift Register
Q.21 Which gate is also called an equality detector?
XOR
XNOR
AND
OR
Explanation - XNOR outputs HIGH when all inputs are equal, thus called an equality detector.
Correct answer is: XNOR
Q.22 Which sequential circuit divides input frequency by 2?
Counter
Flip-Flop
Decoder
Multiplexer
Explanation - A T Flip-Flop toggles state with each clock pulse, effectively dividing the input frequency by 2.
Correct answer is: Flip-Flop
Q.23 Which logic gate is used in parity generation?
AND
OR
XOR
NAND
Explanation - XOR gates are used to generate parity bits as they detect odd/even number of HIGH inputs.
Correct answer is: XOR
Q.24 What is the maximum number of outputs a decoder with 3 inputs can have?
3
6
8
9
Explanation - A decoder with n inputs can have a maximum of 2^n outputs. For 3 inputs, 2^3 = 8.
Correct answer is: 8
Q.25 Which gate is called a minority detector?
AND
OR
NAND
NOR
Explanation - A NOR gate outputs HIGH only when all inputs are LOW, thus detecting the 'minority' state.
Correct answer is: NOR