Combinational Circuits: Master Digital Logic Fundamentals

Question 1

To implement a 1-bit subtractor, which of the following logic circuits is combined with a 1-bit adder?

Accepted Answer

NOT

Answer

NAND

Answer

AND

Answer

OR

Question 2

Which characteristic is unique to asynchronous counters?

Accepted Answer

Asynchronous inputs can affect the state

Answer

Clock-driven operation

Answer

State transitions occur at regular intervals

Answer

Output changes reflect the current state

Question 3

In a 4-bit adder, the carry-in signal for the fourth bit is provided by:

Accepted Answer

Carry-out from the third bit

Answer

Sum of the third bit

Answer

Input A of the third bit

Answer

Input B of the third bit

Question 4

Which type of multiplexer has the largest number of data inputs?

Accepted Answer

16-to-1

Answer

2-to-1

Answer

4-to-1

Answer

8-to-1

Question 5

Which advantage is associated with using multiplexers in digital systems?

Accepted Answer

Increased flexibility in signal routing

Answer

Reduced number of components required

Answer

Faster operation speeds

Answer

Lower power consumption

Question 6

What is the function of a multiplexer?

Accepted Answer

To select a single input signal from multiple sources

Answer

To amplify input signals

Answer

To decode input signals

Answer

To encode input signals

Question 7

What is the purpose of a 4-bit subtractor?

Accepted Answer

To compute the subtraction of two 4-bit binary numbers

Answer

To multiply two 4-bit binary numbers

Answer

To divide two 4-bit binary numbers

Answer

To add two 4-bit binary numbers

Question 8

Which of the following is not a type of multiplexer?

Accepted Answer

Priority encoder

Answer

Data selector

Answer

Channel selector

Answer

Address encoder

Question 9

What is the primary purpose of a parity generator?

Accepted Answer

To generate a parity bit for error detection

Answer

To amplify input signals

Answer

To decode input signals

Answer

To encode input signals

Question 10

Which of the following is the equation for the sum output of a half adder?

Accepted Answer

S = A ⊕ B

Answer

S = A ⋅ B

Answer

C = A + B

Answer

C = A ⊗ B

Question 11

What is the primary distinction between a multiplexer and a demultiplexer?

Accepted Answer

A multiplexer selects one input from multiple sources, while a demultiplexer distributes one input to multiple destinations.

Answer

A demultiplexer selects one input from multiple sources, while a multiplexer distributes one input to multiple destinations.

Answer

They both serve the same purpose.

Answer

They are both used solely in digital signal processing.

Question 12

Convert the binary number 1011 to its decimal equivalent:

Accepted Answer

7

Answer

9

Answer

11

Answer

13

Question 13

Which advantage is provided by utilizing an encoder?

Accepted Answer

Reduction in the number of logic gates required

Answer

Increased operational speed

Answer

Lower power consumption

Answer

Improved reliability

Question 14

What is the fundamental purpose of a subtractor?

Accepted Answer

Subtraction of two numbers

Answer

Addition of two numbers

Answer

Multiplication of two numbers

Answer

Division of two numbers

Question 15

Which logic gate is employed to perform the "NOT" operation?

Accepted Answer

NOT gate

Answer

AND gate

Answer

OR gate

Answer

XOR gate

Question 16

Differentiate between synchronous and asynchronous circuits:

Accepted Answer

Synchronous circuits operate on a common clock signal, whereas asynchronous circuits do not.

Answer

Asynchronous circuits operate on a common clock signal, whereas synchronous circuits do not.

Answer

They operate on identical principles.

Answer

They perform distinct functions.

Question 17

Which feature characterizes a combinational circuit?

Accepted Answer

Its output depends solely on its present inputs

Answer

Feedback loops are present

Answer

Information is stored

Answer

A clock signal is utilized

Question 18

Determine the maximum number of unique outputs possible from a 4-to-1 multiplexer:

Accepted Answer

4

Answer

2

Answer

8

Answer

16

Question 19

What is the purpose of a multiplexer?

Accepted Answer

To select one of several input signals based on a select line.

Answer

To amplify digital signals.

Answer

To convert analog signals to digital signals.

Answer

To store binary data.

Question 20

What is the primary application of a priority encoder?

Accepted Answer

To encode multiple input lines into a binary number while prioritizing certain inputs

Answer

To encode a binary number into a decimal number

Answer

To reduce the number of input lines in a combinational circuit

Answer

To store binary data

Question 21

Which of the following is a key characteristic of combinational circuits?

Accepted Answer

Their outputs depend solely on their current inputs.

Answer

They incorporate memory elements.

Answer

Their operation is sequential.

Answer

They require clock signals for proper functioning.

Question 22

What is a primary purpose of using a truth table in combinational circuit design?

Accepted Answer

To depict all possible input and output combinations for a given circuit.

Answer

To simplify Boolean expressions.

Answer

To analyze circuit behavior under various conditions.

Answer

To simulate the operation of a circuit.

Question 23

Which of the following is **NOT** a type of combinational circuit?

Accepted Answer

Flip-flop

Answer

Adder

Answer

Encoder

Answer

Multiplexer

Question 24

A combinational circuit with 'n' input variables can have a maximum of how many possible output states?

Accepted Answer

2^n

Answer

n

Answer

n^2

Answer

2^(2^n)

Question 25

Consider a 4-bit adder adding two 4-bit numbers, A and B. If A = 1011 and B = 0110, determine the carry-out from the most significant bit (MSB) position.

Accepted Answer

1

Answer

0

Answer

2

Answer

3

Question 26

Which function describes a multiplexer?

Accepted Answer

Selecting one of multiple input signals based on a select line

Answer

Enhancing analog signal strength

Answer

Converting digital signals to analog signals

Answer

Storing binary data

Question 27

Which type of combinational circuit transforms a binary code into a decimal code?

Accepted Answer

Encoder

Answer

Decoder

Answer

Multiplexer

Answer

Demultiplexer

Question 28

In a 4-bit demultiplexer with n data input lines and 2^n output lines, which output line will be activated if the select lines are set to 01?

Accepted Answer

01

Answer

00

Answer

10

Answer

11

Question 29

Which of the following is **not** a fundamental combinational circuit?

Accepted Answer

Multiplier

Answer

Adder

Answer

Decoder

Answer

Multiplexer

Question 30

In a half-adder, the number of input bits is:

Accepted Answer

2

Answer

1

Answer

3

Answer

4

Question 31

What is the primary function of a multiplexer?

Accepted Answer

To select one of several data inputs to pass to the output

Answer

To amplify a digital signal

Answer

To convert an analog signal to a digital signal

Answer

To store digital data

Question 32

In a 4-bit decoder, the number of output lines is:

Accepted Answer

8

Answer

4

Answer

16

Answer

32

Question 33

Which of the following is a characteristic of a combinational circuit?

Accepted Answer

Its output depends solely on its present inputs

Answer

It utilizes feedback to determine its output

Answer

It can store digital data

Answer

It operates in analog mode

Question 34

In a subtractor circuit, the input variables include:

Accepted Answer

Minuend, subtrahend, and borrow-in

Answer

Augend, addend, and carry-in

Answer

Data, select lines, and enable

Answer

Address, data, and write/read control

Question 35

In a decoder circuit, the number of input lines is:

Accepted Answer

Equal to the number of output lines

Answer

Half the number of output lines

Answer

Twice the number of output lines

Answer

Not related to the number of output lines

Question 36

In a decoder, how does the number of input lines influence the number of output lines?

Accepted Answer

The number of output lines is 2 raised to the power of the number of input lines.

Answer

The number of output lines is equal to the number of input lines.

Answer

The number of output lines is half the number of input lines.

Answer

The number of output lines is double the number of input lines.

Question 37

Compare the carry ripple adder and the carry look-ahead adder. Discuss their respective advantages and disadvantages in terms of speed and hardware complexity.

Accepted Answer

Carry look-ahead adder is faster but more complex than carry ripple adder.

Answer

Carry ripple adder is faster but less complex than carry look-ahead adder.

Answer

Both carry ripple adder and carry look-ahead adder have the same speed and complexity.

Answer

Carry ripple adder is slower but more complex than carry look-ahead adder.

Question 38

Which combinational circuit is specifically designed to perform the addition of two binary numbers?

Accepted Answer

Adder

Answer

Flip-flop

Answer

Decoder

Answer

Multiplexer

Question 39

Which circuit is utilized to decode a binary code into a set of distinct output lines?

Accepted Answer

Decoder

Answer

Multiplexer

Answer

Adder

Answer

Encoder

Question 40

A combinational circuit that converts a decimal number into its binary equivalent is called a:

Accepted Answer

Encoder

Answer

Subtractor

Answer

Decoder

Answer

Multiplexer

Question 41

Which circuit is employed to select one of several input signals to be passed to the output?

Accepted Answer

Multiplexer

Answer

Decoder

Answer

Encoder

Answer

Demultiplexer

Question 42

A combinational circuit that performs the subtraction of two binary numbers is referred to as a:

Accepted Answer

Subtractor

Answer

Adder

Answer

Decoder

Question 43

Which circuit is utilized to distribute a single input signal to multiple output lines?

Accepted Answer

Demultiplexer

Answer

Encoder

Answer

Decoder

Question 44

A combinational circuit with n inputs and 2^n outputs is called a:

Accepted Answer

Decoder

Answer

Register

Answer

Multiplexer

Answer

Encoder

Question 45

Which circuit is utilized to represent a binary number as a set of unique weighted outputs?

Accepted Answer

Encoder

Answer

Subtractor

Answer

Multiplexer

Answer

Decoder

Question 46

A combinational circuit that simplifies Boolean expressions is known as a:

Accepted Answer

Logic Gate

Answer

Counter

Answer

Register

Answer

Flip-flop

Question 47

What is the primary function of a combinational circuit?

Accepted Answer

Produces an output based solely on the current input values.

Answer

Generates a sequence of outputs based on a clock signal.

Answer

Stores previous input values for future use.

Question 48

Which of the following is NOT a common type of combinational circuit?

Accepted Answer

Flip-flop

Answer

Adder

Answer

Multiplexer

Answer

Decoder

Question 49

A full adder circuit has three inputs: A, B, and Carry-in (Cin). What is the output Carry-out (Cout) when A = 1, B = 0, and Cin = 1?

Accepted Answer

1

Answer

2

Answer

0

Question 50

A 4-bit binary subtractor is built using full adders and inverters. What is the purpose of inverting the subtrahend before feeding it into the adder?

Accepted Answer

To perform subtraction by adding the two's complement of the subtrahend.

Answer

To convert the binary numbers to decimal.

Answer

To simplify the circuit design.

Question 51

Which of the following is a key advantage of using Karnaugh maps for simplifying Boolean expressions?

Accepted Answer

They visually represent the relationship between input variables and output values.

Answer

They eliminate the need for truth tables.

Answer

They provide a direct conversion from Boolean expressions to circuit diagrams.