Analog to Digital A to D Converter MCQ [Free PDF] - Objective Question Answer for Analog to Digital A to D Converter Quiz

16. In integrating type ADCs, the

A. Input voltage is proportional to input averaged over the integration period
B. Output voltage is proportional to input averaged over the integration period
C. Output voltage is proportional to sum of input voltage
D. Input voltage is proportional to sum of input voltage

Answer: B

Since the integrating type ADC does not require a sample and hold circuit at the input. The change in input during conversion will not affect the output code and is proportional to the value of the input averaged over the integration period.

17. Which type of ADC is chosen for a noisy environment?

A. Successive approximation ADC
B. Dual slope
C. Charge balancing ADC
D. All of the mentioned

Answer: C

The main advantage of these converters is that it is possible to transmit frequency even in noisy environments or in an isolated form.

18. How to overcome the drawback of the charge balancing ADC?

A. By using a precision integrator
B. By using Voltage to frequency converter
C. By using a voltage comparator
D. By using a dual-slope converter

Answer: D

Charge balancing ADC depends upon RC product whose value cannot be easily maintained with temperature and time. This is eliminated using dual-slope ADC as it is independent of R, C, and T.

19. Which among the following has a long conversion time?

A. Servo converter
B. Dual ramp converter
C. Flash converter
D. None of the mentioned

Answer: B

The main disadvantage of dual-slope ADC is the long conversion time. For instance, if 2ⁿ-T=1/50 is used to reject line pick-up, the conversion time will be 20ms.

20. In which application dual slop converter is used.

A. Thermocouple
B. Digital panel meter
C. Weighting scale
D. All of the mentioned

Answer: B

Dual slope converters are particularly suitable for accurate measurement of slow varying signals.

21. A dual slope has the following specifications:

16bit counter; Clock rate =4 MHz; Input voltage=12v; Output voltage =-7v and Capacitor=0.47µF.
If the counters have cycled through 2ⁿ counts, determine the value of the resistor in the integrator.

A. 60kΩ
B. 50kΩ
C. 120kΩ
D. 100kΩ

Answer: A

Time period of the dual slope integrator,

△(t) =t₂-t₁ =2ⁿcounts/clock rate

=2¹⁶/4Mhz=16.38ms.

For integration,

△V_o=(-1/RC.×V×( t₂-t₁)

=> RC = -(12v/-7v) ×16.38ms=28.08ms

∴ R= 28.08ms =59744 ≅60kΩ.

22. A 12-bit dual ramp generation has a maximum output voltage of +12v. Compute the equivalent digital number for the analog signal of +6v.

A. 1000000000
B. 10000000000
C. 1000000000000
D. 100000000000

Answer: D

since V_a =V_R (N/2ⁿ)

so the digital count N= 2ⁿ×(V_a/V_R)

N= 2¹²×(6/12v) = 4096×0.5 =2048.

Binary equivalent for 2048 => 100000000000.

23. Find out the resolution of 8-bit DAC/ADC?

A. 562
B. 625
C. 256
D. 265

Answer: C

The resolution is the value of LSB

Resolution =2ⁿ, where n-> number of bits

∴ Resolution =2⁸=256 possible output values.

24. Non-linearity in the output of the converter is expressed in

A. None of the mentioned
B. Percentage of the reference voltage
C. Percentage of resolution
D. Percentage of full-scale voltage

Answer: D

Non-linearity is the measure of the deviation of actual output (ε) from the ideal straight line output (△). Therefore, it is expressed as a percentage of full-scale voltage (ε/△).

25. A binary input 000 is fed to a 3bit DAC/ADC. The resultant output is 101. Find the type of error?

A. Settling error
B. Gain error
C. Offset error
D. Linearity error

Answer: C

The offset error implies that the output of the DAC is not zero when the binary inputs are all zero.

26. How many equal intervals are present in a 14-bit D-A converter?

A. 16383
B. 4095
C. 65535
D. 1023

Answer: A

A 14-bit D-A converter has 2ⁿ-1 equal interval =2¹⁴-1=16384-1=16383.

27. Resolution of a 6 bit DAC can be stated as

A. Resolution of 1 part in 63
B. 6-bit resolution
C. Resolution of 1.568% of full scale
D. All of the mentioned

Answer: D

Resolution of 6 bit DAC =V_FS% /(2ⁿ-1)

=(V_FS×100)/(2⁶-1) = 1.588% of V_FS and the number of interval is 2⁶-1=63.

=> Thus, resolution of a 6 bit DAC can be stated as a resolution of 1 part in 63.

28. Find the resolution of a 10-bit AD converter for an input range of 10v?

A. 97.7mv
B. 9.77mv
C. 0.977mv
D. 977mv

Answer: B

Resolution (in volts) V_FS /(2ⁿ -1)

= 10 /(2¹⁰ -1)

=10/1023 =9.77mv.

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