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Test: Analog to Digital Converters - Electronics and Communication Engineering (ECE) MCQ


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10 Questions MCQ Test Digital Circuits - Test: Analog to Digital Converters

Test: Analog to Digital Converters for Electronics and Communication Engineering (ECE) 2024 is part of Digital Circuits preparation. The Test: Analog to Digital Converters questions and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus.The Test: Analog to Digital Converters MCQs are made for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Analog to Digital Converters below.
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Test: Analog to Digital Converters - Question 1

For a full-scale voltage of 0-5 V, the resolution of 6 bit ADC is nearest to :

Detailed Solution for Test: Analog to Digital Converters - Question 1
  • Analog-to-Digital Converters (ADCs) transform an analog voltage to a binary number (a series of 1’s and 0’s).
  • Then eventually a digital number (base 10) for reading on a meter, monitor, or chart.
  • The ADC resolution depends upon the number of bits used to represent the digit number
  • As the number of bits increases the resolution of an Analog to Digital Converter improves and the quantization error decreases.
  • The resolution of DAC is a change in analog voltage corresponding to the LSB bit increment at the input. The resolution (R) is calculated as:

where
N is the number of bits
VFs is the full scale deflection 
Given
VFS = 5 V
N = 6
R = 
= 78 mV

Test: Analog to Digital Converters - Question 2

What is the SNR of an ideal 10 bit ADC ?

Detailed Solution for Test: Analog to Digital Converters - Question 2
  • SNR (Signal-to-Noise Ratio) of an ADC (Analog-to-Digital Converter) is a measure of the quality of the ADC's output signal.
  • It represents the ratio of the amplitude of the input signal to the amplitude of the noise present in the output signal. In other words, it is a measure of how much the signal level exceeds the noise level in the output of the ADC.
  • SNR is a calculated value that represents the ratio of RMS signal to RMS noise.
  • If we multiply the log10 of this ratio by 20 to derive SNR in decibels.
  • An ADC’s ideal SNR equals 6.02N + 1.76 dB, where N is the number of bits.

Calculation:
SNR of an 10 bit ADC = 6.02 × 10 + 1.76 = 61.96 dB
Hence the correct answer is option 3.

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Test: Analog to Digital Converters - Question 3

For a 12-bit ADC with voltage range 0-5 V, what will be the resolution?

Detailed Solution for Test: Analog to Digital Converters - Question 3

The ADC resolution is defined as the smallest incremental voltage that can be recognized and thus causes a change in the digital output.
The resolution is given by:

where, R = Resolution
Vref = Maximum analog voltage
n = No. of bits
Calculation
Given, Vref = 5 V
n = 12

R = 1.22 mV

Test: Analog to Digital Converters - Question 4

DA converter is a part of:

Detailed Solution for Test: Analog to Digital Converters - Question 4
  • DA (Digital to analog) converter is a part of the proximity sensor.
  • A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact.
  • A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation and looks for changes in the field or return signal. 
  • The sensor can also be used to detect a wide variety of non-metallic and metallic objects and typically operate over a range of 3 to 30 mm.
  • A capacitive proximity sensor is suitable for a plastic target an inductive proximity sensor always requires a metal target.
Test: Analog to Digital Converters - Question 5

The advantage of using a dual slope ADC in a digital voltmeter is that

Detailed Solution for Test: Analog to Digital Converters - Question 5

The advantage of using a dual-slope ADC in a digital voltmeter is that its accuracy is high. 
Dual slope ADC:

  1. Dual slope integration type ADC is the most accurate type of ADC because of non-dependency on variation in component values caused by noise. 
  2. Dual slope ADC is the slowest ADC among all other ADC's but the advantage of dual-slope ADC is its accuracy. 
  3. These are used in the precision application. 


Advantage of Dual Slope ADC:

  1. High resolution can be achieved by using an accurate count.
  2. Component value variations will have no effect on accuracy.
  3. For instance, the capacitance may change due to temperature variation. But since the charging and discharging processes are done through the same capacitor, the net effect of this capacitance variation is negligible.

Disadvantages:

  • Dual slope ADC is the slowest ADC
Test: Analog to Digital Converters - Question 6

In a successive approximation ADC:

Detailed Solution for Test: Analog to Digital Converters - Question 6

Successive Approximation type DVM:

  • The successive approximation type digital voltmeter works on the principle of balancing the weights in a simple balance.
  • To understand the concept clearly, let us consider whether we want to
  • measure the weight of some unknown quantity of sugar.
  • What do we do? First, we approximate the weight of sugar to some known weight,
  • If the weight of sugar is more than the known weight, then we add some more weight to the known weight.
  • If it is less, then we replace the weight with a lesser value.
  • This process is repeated until the pointer balances the two weights.
  • The successive approximation type DVM uses the same principle.
  • A simple block diagram of SADVM is given below


An elaborated block diagram of SADVM is given below

  • Consists of an input attenuator for selecting the desired range of input voltage and also to attenuate any noise in the given voltage.
  • Selected input is applied to the comparator through a sample and holds circuit.
  • The successive approximation register (SAR) receives its 8-bit input from the ring counter after each clock pulse.
  • This input is applied to the Digital to Analog Converter (DAC) which converts the digital data into an analog voltage.
  • This voltage is applied as a second input to the comparator.
  • The output of the AND gate goes high when there is a positive o/p at the comparator.
  • Finally, the digital output is taken out from the successive approximation register with input voltages other than dc; the input level changes during digitization, and decisions made during conversion are not consistent.
  • To avoid this error, a sample and hold circuit is used and placed in the input directly following the input attenuator.
  • This digital voltmeter is capable of 1000 readings per second.
Test: Analog to Digital Converters - Question 7

Which of the following types of ADC is also known as continuous conversion type ADC?

Detailed Solution for Test: Analog to Digital Converters - Question 7

A successive-approximation ADC is a type of analog-to-digital converter that converts a continuous analog waveform into a discrete digital representation using a binary search through all possible quantization levels before finally converging upon a digital output for each analog voltage conversion.
For an N-bit successive approximation ADC, the conversion time is
= N T
Where T is the time period of the clock pulse.
∴ The conversion time does not depend on the magnitude of the input voltage.

Test: Analog to Digital Converters - Question 8

For a 10-bit digital ramp ADC using 500 kHz clock, the maximum conversion time is

Detailed Solution for Test: Analog to Digital Converters - Question 8

Digital ramp ADC conversion time is given as:

Given:
n = 10
f = 500 kHz
Analysis:

= 2 μs
Conversion time = (2N – 1) Tclk
= (1024 - 1) × 2 μs = 2046 μs

Test: Analog to Digital Converters - Question 9

Find the resolution of a 10-bit AD converter for an input range of 10 V.

Detailed Solution for Test: Analog to Digital Converters - Question 9
  • Analog-to-Digital Converters (ADCs) transform an analog voltage to a binary number (a series of 1’s and 0’s).
  • Then eventually to a digital number (base 10) for reading on a meter, monitor, or chart.
  • The ADC resolution depends upon the number of bits used to represent the digit number. 
  • As the number of bits increases the resolution of an Analog to Digital Converter improves and the quantization error decreases.

The resolution of DAC is a change in analog voltage corresponding to the LSB bit increment at the input.
The resolution (R) is calculated as:

No. of levels = 2N – 1
Vr is reference voltage 'or' Full-scale voltage
Resolution for n – bit A/D converter in percentage will be:

Given: n = 10, VFS = 10 V

= 9.77 mV

Test: Analog to Digital Converters - Question 10

In which of the following types of A/D converters does the conversion time almost double for every bit added to the device?

Detailed Solution for Test: Analog to Digital Converters - Question 10

The conversion time of the countertype A/D counter is (2n−1)Tclk

From above when bit increases, conversion doubles, So the answer is counter type A/D converter.

 

  • Counter type ADC and successive approximate ADC uses DAC
  • Counter type ADC uses linear search and successive approximation type ADC uses binary search
  • Ring counter is used in successive approximation type ADC
  • Flash type ADC is fastest ADC
  • Flash type ADC requires no counter
  • For an n-bit ADC, flash type ADC requires (2n – 1) comparators
  • Dual slope ADC is most accurate
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