MCQOPTIONS
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MCQOPTIONS
This section includes 135 Mcqs, each offering curated multiple-choice questions to sharpen your Digital Electronics knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
A test system using the GPIB is being used to monitor a potentially dangerous crash test from a distance of 200 feet. The engineer decides to have you fabricate a special cable, rather than order one, since all the materials are on hand and the tests are already behind schedule. When the tests are run, the test system is erratic and the data is almost useless. What has gone wrong? |
| A. | The engineer is probably not using the correct data format for the specific instruments being used to collect the data. |
| B. | The GPIB cable is too long; a bus extender should be used. |
| C. | The cable should be shielded and properly grounded. |
| D. | The tests themselves probably produced extraneous signals that confused the instruments, resulting in unusable data. |
| Answer» C. The cable should be shielded and properly grounded. | |
| 102. |
If the same analog signal is to be converted to an 8-bit resolution using a counter-ramp ADC, how many comparator circuits would be used? |
| A. | 1 |
| B. | 8 |
| C. | 127 |
| D. | 255 |
| Answer» B. 8 | |
| 103. |
What is the major advantage of the R/2R ladder D/A converter as compared to a binary-weighted D/A converter? |
| A. | It has fewer parts for the same number of inputs. |
| B. | It is much easier to analyze its operation. |
| C. | It uses only two different resistor values. |
| D. | The virtual ground is eliminated and the circuit is therefore easier to understand and troubleshoot. |
| Answer» D. The virtual ground is eliminated and the circuit is therefore easier to understand and troubleshoot. | |
| 104. |
Resolution in the analog output of a DAC is primarily dependent on the number of input binary bits. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 105. |
What is the accuracy of a D/A converter? |
| A. | It is the reciprocal of the number of discrete steps in the D/A output. |
| B. | It is the comparison between the actual output of the converter and its expected output. |
| C. | It is the converter's ability to resolve between forward and reverse steps when sequenced over its entire range of inputs. |
| D. | It is the deviation between the ideal straight-line output and the actual output of the converter. |
| Answer» C. It is the converter's ability to resolve between forward and reverse steps when sequenced over its entire range of inputs. | |
| 106. |
The output of a basic 4-bit input digital-to-analog converter would be capable of outputting: |
| A. | 16 different values of voltage or current that are not proportional to the input binary number |
| B. | 16 different values of voltage or current that are proportional to the input binary number |
| C. | 32 different values of voltage or current that are not proportional to the input binary number |
| D. | 32 different values of voltage or current that are proportional to the input binary number |
| Answer» C. 32 different values of voltage or current that are not proportional to the input binary number | |
| 107. |
A 4-bit stairstep-ramp A/D converter has a clock frequency of 100 kHz and maximum input voltage of 10 V. |
| A. | The maximum number of samples per second will be 6250. |
| B. | The maximum sample rate will be 100,000 samples/second. |
| C. | The minimum sample rate will be 6250 samples/second. |
| D. | The minimum sample rate will be 100,000 samples/second. |
| Answer» D. The minimum sample rate will be 100,000 samples/second. | |
| 108. |
What is gain error in a DAC? |
| A. | missing codes |
| B. | error in the slope of the output staircase waveform |
| C. | more or less input voltage is required for the first step than what is specified |
| Answer» C. more or less input voltage is required for the first step than what is specified | |
| 109. |
On a binary-weighted D/A converter the least significant binary input ________. |
| A. | connects to the smallest resistor |
| B. | supplies the least voltage |
| C. | connects to a 1 k resistor |
| D. | connects to the largest resistor |
| Answer» E. | |
| 110. |
When the analog input to a tracking A/D converter is at a constant level, the digital output will oscillate. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 111. |
What is the current in the feedback resistor for the circuit given below? |
| A. | 0.625 mA |
| B. | 1.25 mA |
| C. | 1.875 mA |
| D. | 1.625 mA |
| Answer» D. 1.625 mA | |
| 112. |
The delay between a change on the digital input of a DAC and the appearance of the change on the output is called settling time. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 113. |
The quantization error in an analog-to-digital converter can be reduced by: |
| A. | increasing the number of bits in the counter and DAC. |
| B. | decreasing the number of bits in the counter and increasing the number of bits in the DAC. |
| C. | increasing the number of bits in the counter and decreasing the number of bits in the DAC. |
| D. | decreasing the number of bits in the counter and DAC. |
| Answer» B. decreasing the number of bits in the counter and increasing the number of bits in the DAC. | |
| 114. |
________ ADCs have a fixed value of conversion time that is not dependent on the value of the analog input. |
| A. | Substandard |
| B. | Dual |
| C. | Recessive-approximation |
| D. | Successive-approximation |
| Answer» E. | |
| 115. |
What type of DAC is shown below? |
| A. | binary-weighted |
| B. | R-2R ladder |
| Answer» C. | |
| 116. |
What is the purpose of a sample-and-hold circuit? |
| A. | To keep temporary memory |
| B. | To hold a voltage constant so an ADC has time to produce an output |
| C. | To hold a voltage constant so a DAC has time to produce an output |
| D. | To hold data after a multiplexer has selected an output |
| Answer» C. To hold a voltage constant so a DAC has time to produce an output | |
| 117. |
What is the conversion time of a flash converter? |
| A. | 20 s |
| B. | 10 s |
| C. | 1 s |
| D. | The conversion takes place continuously. |
| Answer» E. | |
| 118. |
How many different voltages can be output from a DAC with a 6-bit resolution? |
| A. | 6 |
| B. | 16 |
| C. | 32 |
| D. | 64 |
| Answer» E. | |
| 119. |
What is one advantage to using a parallel-encoded (flash) ADC? |
| A. | less expensive |
| B. | very fast conversion |
| C. | less complicated circuit |
| D. | 1 |
| Answer» C. less complicated circuit | |
| 120. |
There are many applications in which analog data must be digitized and transferred into a computer's memory. The process by which the computer acquires these digitized analog data is referred to as ________. |
| A. | sampling |
| B. | multiplexing |
| C. | data acquisition |
| D. | prescaling |
| Answer» D. prescaling | |
| 121. |
Referring to the given figure, what appears to be wrong, if anything, with the output of the D/A converter? |
| A. | The input signal is probably noisy. |
| B. | There appears to be some nonlinearity in the scope display. |
| C. | The converter has a nonmonotonic output error. |
| D. | It appears that certain input codes are incorrect; double-check the input coding. |
| Answer» D. It appears that certain input codes are incorrect; double-check the input coding. | |
| 122. |
The basic approach to testing D/A converters is to: |
| A. | apply a sequence of binary codes covering the full range of input values to the circuit input while observing the output on an oscilloscope. The output should consist of a linear stairstep ramp. |
| B. | single-step the device through its full input range while checking the output with a DMM. |
| C. | check the output with zero input and then full input. The output of the converter should extend from zero to its maximum value. If so, then everything in between can be assumed to be operating properly. |
| D. | apply the correct input to the analog terminal and then check to see if the proper binary code exists on the digital inputs. |
| Answer» B. single-step the device through its full input range while checking the output with a DMM. | |
| 123. |
A transducer is a device that: |
| A. | converts a physical variable to an electrical variable |
| B. | converts analog data to meaningful data |
| C. | controls a physical variable |
| D. | stores digital data and then processes that data according to a set of specified instructions |
| Answer» B. converts analog data to meaningful data | |
| 124. |
What function is performed by the block labeled X in the given figure? |
| A. | Analog-to-digital conversion |
| B. | Digital-to-analog conversion |
| C. | Audio ON/OFF control |
| D. | Power supply for the audio amplifier |
| Answer» C. Audio ON/OFF control | |
| 125. |
Which of the following describes the basic operation of a single-slope A/D converter. |
| A. | The input voltage is used to set the frequency of a voltage-controlled oscillator (VCO). The VCO quits changing frequency when the input voltage stabilizes. The frequency of the VCO, which is proportional to the analog input voltage, is measured and is displayed on the digital display as a voltage reading. |
| B. | A ramp generator is used to enable a counter through a comparator. When the ramp voltage equals the input voltage the counter is latched and then reset. The counter reading is proportional to the input voltage since the ramp is changing at a constant V/second rate. |
| C. | A ramp voltage and analog input voltage are applied to a comparator. As the input voltage causes the integrating capacitor to charge, it will at some point equal the ramp voltage. The ramp voltage is measured and displayed on the digital panel meter. |
| D. | Any of the above could be correct, depending on the specific type of A/D converter involved. |
| Answer» C. A ramp voltage and analog input voltage are applied to a comparator. As the input voltage causes the integrating capacitor to charge, it will at some point equal the ramp voltage. The ramp voltage is measured and displayed on the digital panel meter. | |
| 126. |
What is the linearity of a D/A converter? |
| A. | It is the reciprocal of the number of discrete steps in the D/A output. |
| B. | It is the comparison between the actual output of the converter and its expected output. |
| C. | It is the converter's ability to resolve between forward and reverse steps when sequenced over its entire range of inputs. |
| D. | It is the deviation between the ideal straight-line output and the actual output of the converter. |
| Answer» E. | |
| 127. |
The process by which a computer acquires digitized analog data is referred to as ________. |
| A. | data acquisition |
| B. | monotonicity |
| C. | analog resolution |
| D. | systematic digital conversion |
| Answer» B. monotonicity | |
| 128. |
The DAC0808 and the MC1408 are very popular and inexpensive 8-bit D/A converters. |
| A. | 1 |
| B. | |
| C. | 1 |
| D. | |
| Answer» B. | |
| 129. |
What is the current in R1 and the current in R2 for the circuit shown below? |
| A. | I1 = 0.416 mA, I2 = 0.416 mA |
| B. | I1 = 0.357 mA, I2 = 0.357 mA |
| C. | I1 = 1.25 mA, I2 = 0.625 mA |
| D. | I1 = 0.625 mA, I2 = 1.25 mA |
| Answer» E. | |
| 130. |
A 4-bit R/2R D/A converter has a reference of 5 V. What is the analog output for the input code 0101? |
| A. | 3.125 V |
| B. | 0.3125 V |
| C. | 0.78125 V |
| D. | –3.125 V |
| Answer» E. | |
| 131. |
Why is a binary-weighted DAC usually limited to 4-bit binary conversion? |
| A. | too many pins on the IC |
| B. | too many op amps needed |
| C. | too many different values of capacitors |
| D. | too many different values of resistors |
| Answer» E. | |
| 132. |
The main advantage of the successive-approximation A/D converter over the counter-ramp A/D converter is its: |
| A. | more complex circuitry |
| B. | less complex circuitry |
| C. | longer conversion time |
| D. | shorter conversion time |
| Answer» E. | |
| 133. |
When comparing the conversions from digital-to-analog and analog-to-digital, the A/D conversion is generally: |
| A. | less complicated but more time consuming than the D/A conversion. |
| B. | more complicated and more time consuming than the D/A conversion. |
| C. | less complicated and less time consuming than the D/A conversion. |
| D. | more complicated but less time consuming than the D/A conversion. |
| Answer» C. less complicated and less time consuming than the D/A conversion. | |
| 134. |
The primary disadvantage of the simultaneous A/D converter is: |
| A. | that it requires the input voltage to be applied to the inputs simultaneously |
| B. | the long conversion time required |
| C. | the large number of output lines required to simultaneously decode the input voltage |
| D. | the large number of comparators required to represent a reasonable sized binary number |
| Answer» E. | |
| 135. |
If an analog signal is to be converted to an 8-bit resolution, how many comparators are used in a parallel-encoded ADC? |
| A. | 127 |
| B. | 128 |
| C. | 255 |
| D. | 256 |
| Answer» E. | |