Interfacing to the Analog World MCQs

Question 1

Inaccurate A/D conversion may be due to:

Accepted Answer

faulty sample-and-hold circuitry

Answer

constant analog input voltage

Answer

linear ramp usage

Answer

intermittent counter inputs

Question 2

What is the resolution, in percent, of a 12-bit DAC?

Accepted Answer

0.049

Answer

8.33

Answer

0.000488

Answer

0.083

Question 3

What circuitry is on an ADC0808 IC?

Accepted Answer

All of the above

Answer

A multiplexer

Answer

An ADC

Answer

A 3-bit select input code

Question 4

What is the maximum conversion time for an 8-bit successive-approximation ADC with a clock frequency of 20 kHz?

Accepted Answer

0.4 ms

Answer

12.8 ms

Answer

6.4 ms

Answer

0.05 ms

Question 5

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?

Accepted Answer

1

Answer

8

Answer

127

Answer

255

Question 6

What is the major advantage of the R/2R ladder D/A converter as compared to a binary-weighted D/A converter?

Accepted Answer

It uses only two different resistor values.

Answer

It has fewer parts for the same number of inputs.

Answer

It is much easier to analyze its operation.

Answer

The virtual ground is eliminated and the circuit is therefore easier to understand and troubleshoot.

Question 7

What is the main disadvantage of the stairstep-ramp A/D converter?

Accepted Answer

The counter must count up from zero at the beginning of each conversion sequence, and the conversion time will vary depending on the input voltage.

Answer

It requires a counter.

Answer

It requires a precision clock in order for the conversion to be reliable.

Answer

All of the above

Question 8

What is the purpose of a sample-and-hold circuit?

Accepted Answer

To hold a voltage constant so an ADC has time to produce an output

Answer

To keep temporary memory

Answer

To hold a voltage constant so a DAC has time to produce an output

Answer

To hold data after a multiplexer has selected an output

Question 9

What is the linearity of a D/A converter?

Accepted Answer

It is the deviation between the ideal straight-line output and the actual output of the converter.

Answer

It is the reciprocal of the number of discrete steps in the D/A output.

Answer

It is the comparison between the actual output of the converter and its expected output.

Answer

It is the converter's ability to resolve between forward and reverse steps when sequenced over its entire range of inputs.