420+ Digital Electronics Solved MCQs

1.

Any number with an exponent of zero is equal to:

A. zero
B. one
C. that number
D. ten
Answer» B. one
2.

In the decimal numbering system, what is the MSD?

A. the middle digit of a stream of numbers
B. the digit to the right of the decimal point
C. the last digit on the right
D. the digit with the most weight
Answer» D. the digit with the most weight
3.

Which of the following statements does NOT describe an advantage of digital technology?

A. the values may vary over a continuous range.
B. the circuits are less affected by noise.
C. the operation can be programmed.
D. information storage is easy.
Answer» A. the values may vary over a continuous range.
4.

The generic array logic (GAL) device is ________.

A. one-time programmable
B. reprogrammable
C. a cmos device
D. reprogrammable and a cmos device
Answer» B. reprogrammable
5.

The range of voltages between VL(max) and VH(min) are ________.

A. unknown
B. unnecessary
C. unacceptable
D. between 2 v and 5 v
Answer» C. unacceptable
6.

What is a digital-to-analog converter?

A. it takes the digital information from an audio cd and converts it to a usable form.
B. it allows the use of cheaper analog techniques, which are always simpler.
C. it stores digital data on a hard drive.
D. it converts direct current to alternating current.
Answer» A. it takes the digital information from an audio cd and converts it to a usable form.
7.

What are the symbols used to represent digits in the binary number system?

A. 0,1
B. 0,1,2
C. 0 through 8
D. 1,2
Answer» A. 0,1
8.

A full subtracter circuit requires ________.

A. two inputs and two outputs
B. two inputs and three outputs
C. three inputs and one output
D. three inputs and two outputs
Answer» D. three inputs and two outputs
9.

The output of an AND gate is LOW ________.

A. all the time
B. when any input is low
C. when any input is high
D. when all inputs are high
Answer» B. when any input is low
10.

Give the decimal value of binary 10010.

A. 610
B. 910
C. 1810
D. 2010
Answer» C. 1810
11.

Parallel format means that:

A. each digital signal has its own conductor.
B. several digital signals are sent on each conductor.
C. both binary and hexadecimal can be used.
D. no clock is needed.
Answer» A. each digital signal has its own conductor.
12.

A decoder converts ________.

A. noncoded information into coded form
B. coded information into noncoded form
C. highs to lows
D. lows to highs
Answer» B. coded information into noncoded form
13.

A DAC changes ________.

A. an analog signal into digital data
B. digital data into an analog signal
C. digital data into an amplified signal
D. none of the above
Answer» B. digital data into an analog signal
14.

The output of a NOT gate is HIGH when ________.

A. the input is low
B. the input is high
C. the input changes from low to high
D. voltage is removed from the gate
Answer» A. the input is low
15.

The output of an OR gate is LOW when ________.

A. all inputs are low
B. any input is low
C. any input is high
D. all inputs are high
Answer» A. all inputs are low
16.

Which of the following is not an analog device?

A. thermocouple
B. current flow in a circuit
C. light switch
D. audio microphone
Answer» C. light switch
17.

A demultiplexer has ________.

A. one data input and a number of selection inputs, and they have several outputs
B. one input and one output
C. several inputs and several outputs
D. several inputs and one output
Answer» A. one data input and a number of selection inputs, and they have several outputs
18.

A flip-flop has ________.

A. one stable state
B. no stable states
C. two stable states
D. none of the above
Answer» C. two stable states
19.

Digital signals transmitted on a single conductor (and a ground) must be transmitted in:

A. slow speed.
B. parallel.
C. analog.
D. serial.
Answer» D. serial.
20.

In a certain digital waveform, the period is four times the pulse width. The duty cycle is ________.

A. 0%
B. 25%
C. 50%
D. 100%
Answer» B. 25%
21.

Select the statement that best describes the parity method of error detection:

A. parity checking is best suited for detecting double-bit errors that occur during the transmission of codes from one location to another.
B. parity checking is not suitable for detecting single-bit errors in transmitted codes.
C. parity checking is best suited for detecting single-bit errors in transmitted codes.
D. parity checking is capable of detecting and correcting errors in transmitted codes.
Answer» C. parity checking is best suited for detecting single-bit errors in transmitted codes.
22.

A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is a(n):

A. ex-nor gate
B. or gate
C. ex-or gate
D. nand gate
Answer» A. ex-nor gate
23.

A logic circuit that provides a HIGH output if one input or the other input, but not both, is HIGH, is a(n):

A. ex-nor gate
B. or gate
C. ex-or gate
D. nand gate
Answer» C. ex-or gate
24.

Identify the type of gate below from the equation

A. ex-nor gate
B. or gate
C. ex-or gate
D. nand gate
Answer» C. ex-or gate
25.

Parity systems are defined as either________ or ________ and will add an extra ________ tothe digital information being transmitted.

A. positive, negative, byte
B. odd, even, bit
C. upper, lower, digit
D. on, off, decimal
Answer» B. odd, even, bit
26.

Which type of gate can be used to add two bits?

A. ex-or
B. ex-nor
C. ex-nand
D. nor
Answer» A. ex-or
27.

Show from the truth table how an exclusive-OR gate can be used to invert the data on one input if the other input is a special control function.

A. using a as the control, when a = 0, x is the same as b. when a = 1, x is the same as b.
B. using a as the control, when a = 0, x is the same as b. when a = 1, x is the inverse of b.
C. using a as the control, when a = 0, x is the inverse of b. when a = 1, x is the same as b.
D. using a as the control, when a = 0, x is the inverse of b. when a = 1, x is the inverse of b.
Answer» B. using a as the control, when a = 0, x is the same as b. when a = 1, x is the inverse of b.
28.

In a flash analog-to-digital converter, the output of each comparator is connected to an input of a ________.

A. decoder
B. priority encoder
C. multiplexer
D. demultiplexer
Answer» B. priority encoder
29.

Which term applies to the maintaining of a given signal level until the next sampling?

A. holding
B. aliasing
C. shannon frequency sampling
D. "stair-stepping"
Answer» A. holding
30.

An op-amp has very ________.

A. high voltage gain
B. high input impedance
C. low output impedance
D. all of the above
Answer» D. all of the above
31.

The dual-slope analog-to-digital converter finds extensive use in ________.

A. digital voltmeters
B. function generators
C. frequency counters
D. all of the above
Answer» D. all of the above
32.

The ADC0804 is an example of a ________.

A. single-slope analog-to-digital converter
B. dual-slope analog-to-digital converter
C. digital-ramp analog-to-digital converter
D. successive-approximation analog-to-digital converter
Answer» D. successive-approximation analog-to-digital converter
33.

In a digital representation of voltages using an 8-bit binary code, how many values can be defined?

A. 16
B. 64
C. 128
D. 256
Answer» D. 256
34.

A 4-bit R/2R ladder digital-to-analog converter uses ________.

A. one resistor value
B. two resistor values
C. three resistor values
D. four resistor values
Answer» B. two resistor values
35.

A binary-weighted-input digital-to-analog converter has a feedback resistor, Rf, of 12 k. If 50 A of current is through the resistor, voltage out of the circuit is ________.

A. 0.6 v
B. –0.6 v
C. 0.1 v
D. –0.1 v
Answer» B. –0.6 v
36.

The resolution of a 6-bit DAC is ________.

A. 63%
B. 64%
C. 15.9%
D. 1.59%
Answer» D. 1.59%
37.

How are unwanted frequencies removed prior to digital conversion?

A. pre-filters
B. digital signal processing
C. sample-and-hold circuits
D. all of the above
Answer» A. pre-filters
38.

Which type of programming is typically used for digital signal processors?

A. assembly language
B. machine language
C. c
D. none of the above
Answer» A. assembly language
39.

Which of the following best defines Nyquist frequency?

A. the frequency of resonance for the filtering circuit
B. the second harmonic
C. the lower frequency limit of sampling
D. the highest frequency component of a given analog signal
Answer» D. the highest frequency component of a given analog signal
40.

Which is not an A/D conversion error?

A. differential nonlinearity
B. missing code
C. incorrect code
D. offset
Answer» A. differential nonlinearity
41.

Settling time is normally defined as the time it takes a DAC to settle within ________.

A. 1/8 lsb of its final value when a change occurs in the input code
B. 1/4 lsb of its final value when a change occurs in the input code
C. 1/2 lsb of its final value when a change occurs in the input code
D. 1 lsb of its final value when a change occurs in the input code
Answer» C. 1/2 lsb of its final value when a change occurs in the input code
42.

Determine the output frequency for a frequency division circuit that contains 12 flip-flops with an input clock frequency of 20.48 MHz.

A. 10.24 khz
B. 5 khz
C. 30.24 khz
D. 15 khz
Answer» B. 5 khz
43.

Which statement BEST describes the operation of a negative-edge-triggered D flip-flop?

A. the logic level at the d input is transferred to q on ngt of clk.
B. the q output is always identical to the clk input if the d input is high.
C. the q output is always identical to the d input when clk = pgt.
D. the q output is always identical to the d input.
Answer» A. the logic level at the d input is transferred to q on ngt of clk.
44.

Propagation delay time, tPLH, is measured from the ________.

A. triggering edge of the clock pulse to the low-to-high transition of the output
B. triggering edge of the clock pulse to the high-to-low transition of the output
C. preset input to the low-to-high transition of the output
D. clear input to the high-to-low transition of the output
Answer» A. triggering edge of the clock pulse to the low-to-high transition of the output
45.

How is a J-K flip-flop made to toggle?

A. j = 0, k = 0
B. j = 1, k = 0
C. j = 0, k = 1
D. j = 1, k = 1
Answer» D. j = 1, k = 1
46.

How many flip-flops are in the 7475 IC?

A. 1
B. 2
C. 4
D. 8
Answer» C. 4
47.

How many flip-flops are required to produce a divide-by-128 device?

A. 1
B. 4
C. 6
D. 7
Answer» D. 7
48.

The ________ circuit overcomes the problem of switching caused by jitter on the inputs.

A. astable multivibrator
B. monostable multivibrator
C. bistable multivibrator
D. schmitt trigger
Answer» D. schmitt trigger
49.

Why would a delay gate be needed for a digital circuit?

A. a delay gate is never needed.
B. to provide for setup times
C. to provide for hold times
D. to provide for setup times and hold times
Answer» D. to provide for setup times and hold times
50.

A Schmitt trigger has VT+ = 2.0 V and VT– = 1.2 V. What is the hysteresis voltage of the Schmitt trigger?

A. 0.4 volt
B. 0.6 volt
C. 0.8 volt
D. 1.2 volts
Answer» C. 0.8 volt
51.

Which of the following circuit parameters would be most likely to limit the maximum operating frequency of a flip-flop?

A. setup and hold time
B. clock pulse high and low time
C. propagation delay time
D. clock transition time
Answer» C. propagation delay time
52.

What is the result of taking more samples during the quantization process?

A. more errors in the analog-to-digital conversion
B. more bit requirements
C. more accurate signal representation
D. more bit requirements and more accurate signal representation
Answer» D. more bit requirements and more accurate signal representation
53.

Which A/D conversion method has a fixed conversion time?

A. single-slope analog-to-digital converter
B. dual-slope analog-to-digital converter
C. digital-ramp analog-to-digital converter
D. successive-approximation analog-to-digital converter
Answer» D. successive-approximation analog-to-digital converter
54.

Which is a typical application of digital signal processing?

A. noise elimination
B. music signal processing
C. image processing
D. all of the above
Answer» D. all of the above
55.

If a DAC has a full-scale, or maximum, output of 12 V and accuracy of 0.1%, then the maximum error for any output voltage is ________.

A. 12 v
B. 120 mv
C. 12 mv
D. 0 v
Answer» C. 12 mv
56.

What do we call the manipulation of an analog signal in a digital domain?

A. analog-to-digital conversion
B. digital-to-analog conversion
C. digital signal processing
D. signal filtering
Answer» B. digital-to-analog conversion
57.

How many address bits are needed to select all memory locations in the 2118 16K × 1 RAM?

A. 8
B. 10
C. 14
D. 16
Answer» C. 14
58.

The check sum method of testing a ROM:

A. indicates if the data in more than one memory location is incorrect.
B. provides a means for locating and correcting data errors in specific memory locations.
C. allows data errors to be pinpointed to a specific memory location.
D. simply indicates that the contents of the rom are incorrect.
Answer» D. simply indicates that the contents of the rom are incorrect.
59.

Refer to the given figures (a) and (b). A logic analyzer is used to check the circuit in figure (a) and displays the waveforms shown in figure (b). The actual analyzer display shows all four data outputs, Q0-Q3. The analyzer's cursor is placed at position X and all four of the data output lines show a LOW level output. What is wrong, if anything, with the circuit?

A. nothing is wrong, according to the display. the outputs are in the open state and should show zero output voltage.
B. the circuit is in the read mode and the outputs, q0-q3, should reflect the contents of the memory at that address. the chip is defective; replace the chip.
C. the circuit is in the mode and should be writing the contents of the selected address to q0–q3.
D. the q0–q3 lines can be either low or high, since the chip is in the tristate mode in which case their level is unpredictable.
Answer» D. the q0–q3 lines can be either low or high, since the chip is in the tristate mode in which case their level is unpredictable.
60.

What is the meaning of RAM, and what is its primary role?

A. readily available memory; it is the first level of memory used by the computer in all of its operations.
B. random access memory; it is memory that can be reached by any sub- system within a computer, and at any time.
C. random access memory; it is the memory used for short-term temporary data storage within the computer.
D. resettable automatic memory; it is memory that can be used and then automatically reset, or cleared, after being read from or written to.
Answer» C. random access memory; it is the memory used for short-term temporary data storage within the computer.
61.

The storage element for a static RAM is the ________.

A. diode
B. resistor
C. capacitor
D. flip-flop
Answer» D. flip-flop
62.

In a DRAM, what is the state of R/W during a read operation?

A. low
B. high
C. hi-z
D. none of the above
Answer» B. high
63.

The condition occurring when two or more devices try to write data to a bus simultaneously is called ________.

A. address decoding
B. bus contention
C. bus collisions
D. address multiplexing
Answer» B. bus contention
64.

The difference between a PLA and a PAL is:

A. the pla has a programmable or plane and a programmable and plane, while the pal only has a programmable and plane.
B. the pal has a programmable or plane and a programmable and plane, while the pla only has a programmable and plane.
C. the pal has more possible product terms than the pla.
D. pals and plas are the same thing.
Answer» A. the pla has a programmable or plane and a programmable and plane, while the pal only has a programmable and plane.
65.

ALM is the acronym for ________.

A. array logic matrix
B. arithmetic logic module
C. asynchronous local modulator
D. adaptive logic module
Answer» D. adaptive logic module
66.

The GAL16V8 has:

A. 16 dedicated inputs.
B. 8 special function pins.
C. 8 pins that are used as inputs or outputs.
D. all of the above
Answer» C. 8 pins that are used as inputs or outputs.
67.

PALs tend to execute ________ logic.

A. sap
B. sop
C. pla
D. spd
Answer» B. sop
68.

How many pins are in an EDF10K70 package?

A. 70
B. 140
C. 240
D. 532
Answer» C. 240
69.

Convert hexadecimal value 16 to decimal.

A. 2210
B. 1610
C. 1010
D. 2010
Answer» A. 2210
70.

Convert the following decimal number to 8-bit binary.

A. 101110112
B. 110111012
C. 101111012
D. 101111002
Answer» A. 101110112
71.

Convert binary 111111110010 to hexadecimal.

A. ee216
B. ff216
C. 2fe16
D. fd216
Answer» B. ff216
72.

Convert the binary number 1001.00102 to decimal.

A. 90.125
B. 9.125
C. 125
D. 12.5
Answer» B. 9.125
73.

One hex digit is sometimes referred to as a(n):

A. byte
B. nibble
C. grouping
D. instruction
Answer» B. nibble
74.

Which of the following is the most widely used alphanumeric code for computer input and output?

A. gray
B. ascii
C. parity
D. ebcdic
Answer» B. ascii
75.

If a typical PC uses a 20-bit address code, how much memory can the CPU address?

A. 20 mb
B. 10 mb
C. 1 mb
D. 580 mb
Answer» C. 1 mb
76.

Convert 59.7210 to BCD.

A. 111011
B. 01011001.01110010
C. 1110.11
D. 0101100101110010
Answer» B. 01011001.01110010
77.

Convert 8B3F16 to binary.

A. 35647
B. 011010
C. 1011001111100011
D. 1000101100111111
Answer» D. 1000101100111111
78.

Which is typically the longest: bit, byte, nibble, word?

A. bit
B. byte
C. nibble
D. word
Answer» D. word
79.

Assign the proper odd parity bit to the code 111001.

A. 1111011
B. 1111001
C. 0111111
D. 0011111
Answer» B. 1111001
80.

Convert decimal 64 to binary.

A. 01010010
B. 01000000
C. 00110110
D. 01001000
Answer» B. 01000000
81.

Convert hexadecimal value C1 to binary.

A. 11000001
B. 1000111
C. 111000100
D. 111000001
Answer» A. 11000001
82.

The given hexadecimal number (1E.53)16 is equivalent to                          

A. (35.684)8
B. (36.246)8
C. (34.340)8
D. (35.599)8
Answer» B. (36.246)8
83.

The octal number (651.124)8 is equivalent to              

A. 16
B. (1b0.10)16
C. (1a8.a3)16
D. (1b0.b0)16
Answer» A. 16
84.

The octal equivalent of the decimal number (417)10 is            

A. (641)8
B. (619)8
C. (640)8
D. (598)8
Answer» A. (641)8
85.

Convert the hexadecimal number (1E2)16 to decimal:

A. 480
B. 483
C. 482
D. 484
Answer» C. 482
86.

(170)10 is equivalent to

A. (fd)16
B. (df)16
C. (aa)16
D. (af)16
Answer» C. (aa)16
87.

Convert the binary number (01011.1011)2 into decimal:

A. (11.6875)10
B. (11.5874)10
C. (10.9876)10
D. (10.7893)10
Answer» A. (11.6875)10
88.

1011)2 = (11.6875)10

A. (111101)2
B. (010100)2
C. (111100)2
D. (101010)2
Answer» B. (010100)2
89.

On addition of +38 and -20 using 2’s complement, we get                          

A. 11110001
B. 100001110
C. 010010
D. 110101011
Answer» C. 010010
90.

On addition of -46 and +28 using 2’s complement, we get                          

A. 00101110
B. 0101110
C. 00101111
D. 1001111
Answer» B. 0101110
91.

On subtracting +28 from +29 using 2’s complement, we get                          

A. 11111010
B. 111111001
C. 100001
D. 1
Answer» D. 1
92.

The decimal number 10 is represented in its BCD form as                      

A. 10100000
B. 01010111
C. 00010000
D. 00101011
Answer» C. 00010000
93.

When numbers, letters or words are represented by a special group of symbols, this process is called                      

A. decoding
B. encoding
C. digitizing
D. inverting
Answer» B. encoding
94.

Carry out BCD subtraction for (68) – (61) using 10’s complement method.

A. 00000111
B. 01110000
C. 100000111
D. 011111000
Answer» A. 00000111
95.

How many bits would be required to encode decimal numbers 0 to 9999 in straight binary codes?

A. 12
B. 14
C. 16
D. 18
Answer» B. 14
96.

The decimal equivalent of the excess-3 number 110010100011.01110101 is

A. 970.42
B. 1253.75
C. 861.75
D. 1132.87
Answer» A. 970.42
97.

In boolean algebra, the OR operation is performed by which properties?

A. associative properties
B. commutative properties
C. distributive properties
D. all of the mentioned
Answer» D. all of the mentioned
98.

The expression for Absorption law is given by                    

A. a + ab = a
B. a + ab = b
C. ab + aa’ = a
D. a + b = b + a
Answer» A. a + ab = a
99.

According to boolean law: A + 1 = ?

A. 1
B. a
C. 0
D. a’
Answer» A. 1
100.

The involution of A is equal to                    

A. a
B. a’
C. 1
D. 0
Answer» A. a
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