Digital Electronics-Interfacing to the Analog World
Digital Electronics-Interfacing to the Analog World
11. The basic approach to testing D/A converters is to:
- 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.
- single-step the device through its full input range while checking the output with a DMM.
- 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.
- apply the correct input to the analog terminal and then check to see if the proper binary code exists on the digital inputs.
12. One major difference between a counter-ramp A/D converter and a successive-approximation converter is:
- the counter-ramp A/D converter is much faster than the successive-approximation converter
- with the successive-approximation converter the final binary result is always slightly less than the equivalent analog input, whereas with the counter-ramp A/D converter it is slightly more
- with the successive-approximation converter the final binary result is always slightly more than the equivalent analog input, whereas with the counter-ramp A/D converter it is slightly less
- none of the above
13. Which of the following characterizes an analog quantity?
- Discrete levels represent changes in a quantity.
- Its values follow a logarithmic response curve.
- It can be described with a finite number of steps.
- It has a continuous set of values over a given range.
14. What is the resolution of a D/A converter?
- the comparison between the actual output of the converter and its expected output
- the reciprocal of the number of discrete steps in the D/A output
- the deviation between the ideal straight-line output and the actual output of the converter
- the ability to resolve between forward and reverse steps when sequenced over its entire range
15. The practical use of binary-weighted digital-to-analog converters is limited to:
- R/2R ladder D/A converters
- 4-bit D/A converters
- 8-bit D/A converters
- op-amp comparators
16. What is the major advantage of the R/2R ladder DAC as compared to a binary-weighted-input DAC?
- It has fewer parts for the same number of inputs.
- It is much easier to analyze its operation.
- It uses only two different resistor values.
- The virtual ground is eliminated and the circuit is therefore easier to understand and troubleshoot.
17. An analog-to-digital converter has a four-bit output. How many analog values can it represent?
- 4
- 1/4
- 16
- 0.0625
18. When comparing the conversions from digital-to-analog and analog-to-digital, the A/D conversion is generally:
- less complicated but more time consuming than the D/A conversion.
- more complicated and more time consuming than the D/A conversion.
- less complicated and less time consuming than the D/A conversion.
- more complicated but less time consuming than the D/A conversion.
19. Which of the statements below best describes the basic operation of a dual-slope A/D converter?
- 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 di
- 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/s
- 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.
- Two ramps are generated: one by the input voltage and the other by a reference voltage. The input voltage ramp charges the integrating capacitor, while the reference voltage discharges the capacitor and enables the counter until the capacitor is discharge
20. The output of a basic 4-bit input digital-to-analog converter would be capable of outputting:
- 16 different values of voltage or current that are not proportional to the input binary number
- 16 different values of voltage or current that are proportional to the input binary number
- 32 different values of voltage or current that are not proportional to the input binary number
- 32 different values of voltage or current that are proportional to the input binary number