interfacing-to-the-analog-world digital-electronics question and answers -Page 5

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1. A certain digital-to-analog converter has a step size of 0.25 V and a full-scale output of 7.75 V. Determine the percent of resolution and the number of input binary bits.
Options
A. 31%, 4 bits
B. 3.23%, 4 bits
C. 31%, 5 bits
D. 3.23%, 5 bits

2. What is gain error in a DAC?
Options
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

3. Which of the following describes the basic operation of a single-slope A/D converter.
Options
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.

6. Referring to the given figure, what appears to be wrong, if anything, with the D/A converter and what should be done to correct the problem?
Options
A. There is nothing wrong with the converter.
B. There is an offset error; if no provision is made for adjusting the offset, the op-amp may need to be changed.
C. There is a nonlinearity error; the op-amp must be changed.
D. The power supply voltage appears to be too high; adjust the power supply to the correct value.

7. What is the major advantage of the R/2R ladder DAC as compared to a binary-weighted-input DAC?
Options
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.

8. The output of a basic 4-bit input digital-to-analog converter would be capable of outputting:
Options
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

9. The quantization error in an analog-to-digital converter can be reduced by:
Options
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.

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