420+ Digital Electronics Solved MCQs

101.

DeMorgan’s theorem states that                    

A. (ab)’ = a’ + b’
B. (a + b)’ = a’ * b
C. a’ + b’ = a’b’
D. (ab)’ = a’ + b
Answer» A. (ab)’ = a’ + b’
102.

(A + B)(A’ * B’) = ?

A. 1
B. 0
C. ab
D. ab’
Answer» B. 0
103.

Complement of the expression A’B + CD’ is                    

A. (a’ + b)(c’ + d)
B. (a + b’)(c’ + d)
C. (a’ + b)(c’ + d)
D. (a + b’)(c + d’)
Answer» B. (a + b’)(c’ + d)
104.

Simplify Y = AB’ + (A’ + B)C.

A. ab’ + c
B. ab + ac
C. a’b + ac’
D. ab + a
Answer» A. ab’ + c
105.

The boolean function A + BC is a reduced form of                          

A. ab + bc
B. (a + b)(a + c)
C. a’b + ab’c
D. (a + c)b
Answer» B. (a + b)(a + c)
106.

A                          is a circuit with only one output but can have multiple inputs.

A. logic gate
B. truth table
C. binary circuit
D. boolean circuit
Answer» A. logic gate
107.

There are 5 universal gates.

A. true
B. false
Answer» B. false
108.

The Output is LOW if any one of the inputs is HIGH in case of a                    gate.

A. nor
B. nand
C. or
D. and
Answer» B. nand
109.

The complement of the input given is obtained in case of:

A. nor
B. and+nor
C. not
D. ex-or
Answer» C. not
110.

How many AND gates are required to realize the following expression Y=AB+BC?

A. 4
B. 8
C. 1
D. 2
Answer» D. 2
111.

Number of outputs in a half adder

A. 1
B. 2
C. 3
D. 0
Answer» B. 2
112.

The                  gate is an OR gate followed by a NOT gate.

A. nand
B. exor
C. nor
D. exnor
Answer» C. nor
113.

The expression of a NAND gate is               

A. a.b
B. a’b+ab’
C. (a.b)’
D. (a+b)’
Answer» C. (a.b)’
114.

Which of the following correctly describes the distributive law.

A. ( a+b)(c+d)=ab+cd
B. (a+b).c=ac+bc
C. (ab)(a+b)=ab
D. (a.b)c=ac.ab
Answer» B. (a+b).c=ac+bc
115.

The logical sum of two or more logical product terms is called                      

A. sop
B. pos
C. or operation
D. nand operation
Answer» A. sop
116.

The expression Y=(A+B)(B+C)(C+A) shows the                    operation.

A. and
B. pos
C. sop
D. nand
Answer» B. pos
117.

The canonical sum of product form of the function y(A,B) = A + B is                      

A. ab + bb + a’a
B. ab + ab’ + a’b
C. ba + ba’ + a’b’
D. ab’ + a’b + a’b’
Answer» B. ab + ab’ + a’b
118.

A variable on its own or in its complemented form is known as a

A. product term
B. literal
C. sum term
D. word
Answer» B. literal
119.

Maxterm is the sum of                      of the corresponding Minterm with its literal complemented.

A. terms
B. words
C. numbers
D. nibble
Answer» A. terms
120.

Canonical form is a unique way of representing                          

A. sop
B. minterm
C. boolean expressions
D. pos
Answer» C. boolean expressions
121.

There are                            Minterms for 3 variables (a, b, c).

A. 0
B. 2
C. 8
D. 1
Answer» C. 8
122.

                           expressions can be implemented using either (1) 2-level AND- OR logic circuits or (2) 2-level NAND logic circuits.

A. pos
B. literals
C. sop
D. pos
Answer» C. sop
123.

There are              cells in a 4-variable K- map.

A. 12
B. 16
C. 18
D. 8
Answer» B. 16
124.

The prime implicant which has at least one element that is not present in any other implicant is known as                        

A. essential prime implicant
B. implicant
C. complement
D. prime complement
Answer» A. essential prime implicant
125.

Product-of-Sums expressions can be implemented using                        

A. 2-level or-and logic circuits
B. 2-level nor logic circuits
C. 2-level xor logic circuits
D. both 2-level or-and and nor logic circuits
Answer» D. both 2-level or-and and nor logic circuits
126.

Each product term of a group, w’.x.y’ and w.y, represents the                         in that group.

A. input
B. pos
C. sum-of-minterms
D. sum of maxterms
Answer» C. sum-of-minterms
127.

It should be kept in mind that don’t care terms should be used along with the terms that are present in                        

A. minterms
B. expressions
C. k-map
D. latches
Answer» A. minterms
128.

Using the transformation method you can realize any POS realization of OR-AND with only.

A. xor
B. nand
C. and
D. nor
Answer» D. nor
129.

In case of XOR/XNOR simplification we have to look for the following

A. diagonal adjacencies
B. offset adjacencies
C. straight adjacencies
D. both diagonal and offset adjencies
Answer» D. both diagonal and offset adjencies
130.

In which of the following gates the output is 1 if and only if at least one input is 1?

A. and
B. nor
C. nand
D. or
Answer» D. or
131.

The time required for a gate or inverter to change its state is called                      

A. rise time
B. decay time
C. propagation time
D. charging time
Answer» C. propagation time
132.

Odd parity of word can be conveniently tested by                        

A. or gate
B. and gate
C. nand gate
D. xor gate
Answer» D. xor gate
133.

The number of full and half adders are required to add 16-bit number is                      

A. 8 half adders, 8 full adders
B. 1 half adders, 15 full adders
C. 16 half adders, 0 full adders
D. 4 half adders, 12 full adders
Answer» B. 1 half adders, 15 full adders
134.

An OR gate can be imagined as

A. switches connected in series
B. switches connected in parallel
C. mos transistor connected in series
D. bjt transistor connected in series
Answer» B. switches connected in parallel
135.

In parts of the processor, adders are used to calculate                          

A. addresses
B. table indices
C. increment and decrement operators
D. all of the mentioned
Answer» D. all of the mentioned
136.

How many full adders are required to construct an m-bit parallel adder?

A. m/2
B. m
C. m-1
D. m+1
Answer» C. m-1
137.

In which operation carry is obtained?

A. subtraction
B. addition
C. multiplication
D. both addition and subtraction
Answer» B. addition
138.

If A and B are the inputs of a half adder, the sum is given by                      

A. a and b
B. a or b
C. a xor b
D. a ex-nor b
Answer» C. a xor b
139.

If A and B are the inputs of a half adder, the carry is given by                      

A. a and b
B. a or b
C. a xor b
D. a ex-nor b
Answer» A. a and b
140.

Half-adders have a major limitation in that they cannot                      

A. accept a carry bit from a present stage
B. accept a carry bit from a next stage
C. accept a carry bit from a previous stage
D. accept a carry bit from the following stages
Answer» C. accept a carry bit from a previous stage
141.

The difference between half adder and full adder is                      

A. half adder has two inputs while full adder has four inputs
B. half adder has one output while full adder has two outputs
C. half adder has two inputs while full adder has three inputs
D. all of the mentioned
Answer» C. half adder has two inputs while full adder has three inputs
142.

If A, B and C are the inputs of a full adder then the sum is given by                      

A. a and b and c
B. a or b and c
C. a xor b xor c
D. a or b or c
Answer» C. a xor b xor c
143.

If A, B and C are the inputs of a full adder then the carry is given by                      

A. a and b or (a or b) and c
B. a or b or (a and b) c
C. (a and b) or (a and b)c
D. a xor b xor (a xor b) and c
Answer» A. a and b or (a or b) and c
144.

How many AND, OR and EXOR gates are required for the configuration of full

A. 1, 2, 2
B. 2, 1, 2
C. 3, 1, 2
D. 4, 0, 1
Answer» B. 2, 1, 2
145.

Half subtractor is used to perform subtraction of                        

A. 2 bits
B. 3 bits
C. 4 bits
D. 5 bits
Answer» A. 2 bits
146.

How many outputs are required for the implementation of a subtractor?

A. 1
B. 2
C. 3
D. 4
Answer» B. 2
147.

Let the input of a subtractor is A and B then what the output will be if A = B?

A. 0
B. 1
C. a
D. b
Answer» A. 0
148.

Let A and B is the input of a subtractor then the output will be                        

A. a xor b
B. a and b
C. a or b
D. a exnor b
Answer» A. a xor b
149.

Let A and B is the input of a subtractor then the borrow will be                        

A. a and b’
B. a’ and b
C. a or b
D. a and b
Answer» B. a’ and b
150.

What does minuend and subtrahend denotes in a subtractor?

A. their corresponding bits of input
B. its outputs
C. its inputs
D. borrow bits
Answer» C. its inputs
151.

Full subtractor is used to perform subtraction of                        

A. 2 bits
B. 3 bits
C. 4 bits
D. 8 bits
Answer» B. 3 bits
152.

The output of a full subtractor is same as

A. half adder
B. full adder
C. half subtractor
D. decoder
Answer» B. full adder
153.

The full subtractor can be implemented using                        

A. two xor and an or gates
B. two half subtractors and an or gate
C. two multiplexers and an and gate
D. two comparators and an and gate
Answer» B. two half subtractors and an or gate
154.

Why XOR gate is called an inverter?

A. because of the same input
B. because of the same output
C. it behaves like a not gate
D. it behaves like a and gate
Answer» C. it behaves like a not gate
155.

Controlled buffers can be useful

A. to control the circuit’s output into the bus
B. in comparison of component’s output with its input
C. in increasing the output from its low input
D. all of the mentioned
Answer» A. to control the circuit’s output into the bus
156.

A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is

A. ex-nor gate
B. or gate
C. ex-or gate
D. nand gate
Answer» A. ex-nor gate
157.

What is the first thing you will need if you are going to use a macro-function?

A. a complicated design project
B. an experienced design engineer
C. good documentation
D. experience in hdl
Answer» D. experience in hdl
158.

What is the major difference between half- adders and full-adders?

A. full-adders are made up of two half-adders
B. full adders can handle double-digit numbers
C. full adders have a carry input capability
D. half adders can handle only single-digit numbers
Answer» C. full adders have a carry input capability
159.

The binary subtraction of 0 – 0 = ?

A. difference = 0, borrow = 0
B. difference = 1, borrow = 0
C. difference = 1, borrow = 1
D. difference = 0, borrow = 1
Answer» A. difference = 0, borrow = 0
160.

How many basic binary subtraction operations are possible?

A. 1
B. 4
C. 3
D. 2
Answer» B. 4
161.

When performing subtraction by addition in the 2’s-complement system                          

A. the minuend and the subtrahend are both changed to the 2’s-complement
B. the minuend is changed to 2’s- complement and the subtrahend is left in its original form
C. the minuend is left in its original form and the subtrahend is changed to its 2’s- complement
D. the minuend and subtrahend are both left in their original form
Answer» C. the minuend is left in its original form and the subtrahend is changed to its 2’s- complement
162.

What are the two types of basic adder circuits?

A. sum and carry
B. half-adder and full-adder
C. asynchronous and synchronous
D. one and two’s-complement
Answer» B. half-adder and full-adder
163.

Which of the following is correct for full adders?

A. full adders have the capability of directly adding decimal numbers
B. full adders are used to make half adders
C. full adders are limited to two inputs since there are only two binary digits
D. in a parallel full adder, the first stage may be a half adder
Answer» D. in a parallel full adder, the first stage may be a half adder
164.

The selector inputs to an arithmetic/logic unit (ALU) determine the                          

A. selection of the ic
B. arithmetic or logic function
C. data word selection
D. clock frequency to be used
Answer» B. arithmetic or logic function
165.

The inverter can be produced with how many NAND gates?

A. 2
B. 1
C. 3
D. 4
Answer» B. 1
166.

What are carry generate combinations?

A. if all the input are same then a carry is generated
B. if all of the output are independent of the inputs
C. if all of the input are dependent on the output
D. if all of the output are dependent on the input
Answer» B. if all of the output are independent of the inputs
167.

How many shift registers are used in a 4 bit serial adder?

A. 4
B. 3
C. 2
D. 5
Answer» C. 2
168.

A D flip-flop is used in a 4-bit serial adder, why?

A. it is used to invert the input of the full adder
B. it is used to store the output of the full adder
C. it is used to store the carry output of the full adder
D. it is used to store the sum output of the full adder
Answer» C. it is used to store the carry output of the full adder
169.

What is ripple carry adder?

A. the carry output of the lower order stage is connected to the carry input of the next higher order stage
B. the carry input of the lower order stage is connected to the carry output of the next higher order stage
C. the carry output of the higher order stage is connected to the carry input of the next lower order stage
D. the carry input of the higher order stage is connected to the carry output of the lower order stage
Answer» A. the carry output of the lower order stage is connected to the carry input of the next higher order stage
170.

If minuend = 0, subtrahend = 1 and borrow input = 1 in a full subtractor then the borrow output will be                      

A. 0
B. 1
C. floating
D. high impedance
Answer» B. 1
171.

The decimal number system represents the decimal number in the form of                          

A. hexadecimal
B. binary coded
C. octal
D. decimal
Answer» B. binary coded
172.

29 input circuit will have total of

A. 32 entries
B. 128 entries
C. 256 entries
D. 512 entries
Answer» D. 512 entries
173.

BCD adder can be constructed with 3 IC packages each of                          

A. 2 bits
B. 3 bits
C. 4 bits
D. 5 bits
Answer» C. 4 bits
174.

The output sum of two decimal digits can be represented in                          

A. gray code
B. excess-3
C. bcd
D. hexadecimal
Answer» C. bcd
175.

The addition of two decimal digits in BCD can be done through                          

A. bcd adder
B. full adder
C. ripple carry adder
D. carry look ahead
Answer» A. bcd adder
176.

3 bits full adder contains                          

A. 3 combinational inputs
B. 4 combinational inputs
C. 6 combinational inputs
D. 8 combinational inputs
Answer» D. 8 combinational inputs
177.

The simplified expression of full adder carry is                          

A. c = xy+xz+yz
B. c = xy+xz
C. c = xy+yz
D. c = x+y+z
Answer» A. c = xy+xz+yz
178.

Complement of F’ gives back                      

A. f’
B. f
C. ff
D. ff’
Answer» B. f
179.

Decimal digit in BCD can be represented by                          

A. 1 input line
B. 2 input lines
C. 3 input lines
D. 4 input lines
Answer» D. 4 input lines
180.

The number of logic gates and the way of their interconnections can be classified as

A. logical network
B. system network
C. circuit network
D. gate network
Answer» A. logical network
181.

What is a multiplexer?

A. it is a type of decoder which decodes several inputs and gives one output
B. a multiplexer is a device which converts many signals into one
C. it takes one input and results into many output
D. it is a type of encoder which decodes several inputs and gives one output
Answer» B. a multiplexer is a device which converts many signals into one
182.

Which combinational circuit is renowned for selecting a single input from multiple inputs & directing the binary information to output line?

A. data selector
B. data distributor
C. both data selector and data distributor
D. demultiplexer
Answer» A. data selector
183.

It is possible for an enable or strobe input to undergo an expansion of two or more MUX ICs to the digital multiplexer with the proficiency of large number of                        

A. inputs
B. outputs
C. selection lines
D. enable lines
Answer» A. inputs
184.

Which is the major functioning responsibility of the multiplexing combinational circuit?

A. decoding the binary information
B. generation of all minterms in an output function with or-gate
C. generation of selected path between multiple sources and a single destination
D. encoding of binary information
Answer» C. generation of selected path between multiple sources and a single destination
185.

6 MULTIPLEXER

A. to apply vcc
B. to connect ground
C. to active the entire chip
D. to active one half of the chip
Answer» C. to active the entire chip
186.

One multiplexer can take the place of

A. several ssi logic gates
B. combinational logic circuits
C. several ex-nor gates
D. several ssi logic gates or combinational logic circuits
Answer» D. several ssi logic gates or combinational logic circuits
187.

A digital multiplexer is a combinational circuit that selects                        

A. one digital information from several sources and transmits the selected one
B. many digital information and convert them into one
C. many decimal inputs and transmits the selected information
D. many decimal outputs and accepts the selected information
Answer» A. one digital information from several sources and transmits the selected one
188.

If the number of n selected input lines is equal to 2^m then it requires            select lines.

A. 2
B. m
C. n
D. 2n
Answer» B. m
189.

How many select lines would be required for an 8-line-to-1-line multiplexer?

A. 2
B. 4
C. 8
D. 3
Answer» D. 3
190.

A basic multiplexer principle can be demonstrated through the use of a

A. single-pole relay
B. dpdt switch
C. rotary switch
D. linear stepper
Answer» C. rotary switch
191.

How many NOT gates are required for the construction of a 4-to-1 multiplexer?

A. 3
B. 4
C. 2
D. 5
Answer» C. 2
192.

In the given 4-to-1 multiplexer, if c1 = 0 and c0 = 1 then the output M is                        

A. x0
B. x1
C. x2
D. x3
Answer» B. x1
193.

The enable input is also known as

A. select input
B. decoded input
C. strobe
D. sink
Answer» C. strobe
194.

The word demultiplex means                        

A. one into many
B. many into one
C. distributor
D. one into many as well as distributor
Answer» D. one into many as well as distributor
195.

Why is a demultiplexer called a data distributor?

A. the input will be distributed to one of the outputs
B. one of the inputs will be selected for the output
C. the output will be distributed to one of the inputs
D. single input to single output
Answer» A. the input will be distributed to one of the outputs
196.

Most demultiplexers facilitate which type of conversion?

A. decimal-to-hexadecimal
B. single input, multiple outputs
C. ac to dc
D. odd parity to even parity
Answer» B. single input, multiple outputs
197.

In 1-to-4 demultiplexer, how many select lines are required?

A. 2
B. 3
C. 4
D. 5
Answer» A. 2
198.

In a multiplexer the output depends on its

A. data inputs
B. select inputs
C. select outputs
D. enable pin
Answer» B. select inputs
199.

In 1-to-4 multiplexer, if C1 = 0 & C2 = 1, then the output will be                        

A. y0
B. y1
C. y2
D. y3
Answer» B. y1
200.

In 1-to-4 multiplexer, if C1 = 1 & C2 = 1, then the output will be                        

A. y0
B. y1
C. y2
D. y3
Answer» D. y3
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