Interfacing to the Analog World MCQs

Question 1

If an analog signal is to be converted to an 8-bit resolution, how many comparators are used in a parallel-encoded ADC?

Accepted Answer

256

Answer

127

Answer

128

Answer

255

Question 2

A transducer is a device that:

Accepted Answer

converts a physical variable to an electrical variable

Answer

converts analog data to meaningful data

Answer

controls a physical variable

Answer

stores digital data and then processes that data according to a set of specified instructions

Question 3

How many different voltages can be output from a DAC with a 6-bit resolution?

Accepted Answer

64

Answer

6

Answer

16

Answer

32

Question 4

A 4-bit R/2R D/A converter has a reference of 5 V. What is the analog output for the input code 0101?

Accepted Answer

–3.125 V

Answer

3.125 V

Answer

0.3125 V

Answer

0.78125 V

Question 5

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

Accepted Answer

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.

Answer

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.

Answer

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.

Answer

Any of the above could be correct, depending on the specific type of A/D converter involved.

Question 6

The main advantage of the successive-approximation A/D converter over the counter-ramp A/D converter is its:

Accepted Answer

shorter conversion time

Answer

more complex circuitry

Answer

less complex circuitry

Answer

longer conversion time

Question 7

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

Accepted Answer

increasing the number of bits in the counter and DAC.

Answer

decreasing the number of bits in the counter and increasing the number of bits in the DAC.

Answer

increasing the number of bits in the counter and decreasing the number of bits in the DAC.

Answer

decreasing the number of bits in the counter and DAC.

Question 8

One disadvantage of the tracking A/D converter is:

Accepted Answer

that the binary output will oscillate between two binary states when the analog input is constant.

Answer

that it requires two counters—one for up and one for down.

Answer

the need for an accurate clock reference for the counter.

Answer

the need for a latch and its associated control circuit.

Question 9

If the range of output voltage of a 6-bit DAC is 0 to 15 volts, what is the step voltage of the output?

Accepted Answer

0.234 volt/step

Answer

0.117 volt/step

Answer

2.13 volts/step

Answer

4.26 volts/step