Data Converters MCQ Quiz in मल्याळम - Objective Question with Answer for Data Converters - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

Digital ramp ADC conversion time is given as:

 \(= \left( {{2^N} - 1} \right){T_{clk}} \)

Given:

n = 10

f = 500 kHz

Analysis:

\({T_{clk}} = \frac{1}{{500\; \times \;{{10}^3}}}\) 

= 2 μs

Conversion time = (2^N – 1) T_clk

= (1024 - 1) × 2 μs = 2046 μs

Important Points

 The conversion time of different types of n-bit ADC is shown :

Concept:

Maximum error (E_r) of D/A is given as,

E_r = (V_FS x Accuracy)

Where,

V_FS: full-scale input voltage

Calculation:

Given: V_fS = 5V , Accuracy= 0.2%

\({E_r} = \frac{{5 \times 0.2}}{{100}}\)

\({E_r} = \frac{1}{{100}} \)

E_r = 10 mV

\The correct answer is option 2):(Flash type)

Concept:

Flash ADC (Fastest)

• The flash ADC is the fastest type available. A flash ADC uses comparators, one per voltage step, and a string of resistors.
• Flash-type ADC requires no counter For an n-bit ADC, flash-type ADC requires (2ⁿ – 1) comparators
• A 4-bit ADC will have 15 comparators, and an 8-bit ADC will have 255 comparators.
• The following figure shows a 3-bit flash ADC circuit.

• It is formed of a series of comparators, each one comparing the input signal to a unique reference voltage.
• The comparator outputs connect to the inputs of a priority encoder circuit, which then produces a binary output.
• Vref is a stable reference voltage provided by a precision voltage regulator as part of the converter circuit.
• As the analog input voltage exceeds the reference voltage at each comparator, the comparator outputs will sequentially saturate to a high state.
• The priority encoder generates a binary number based on the highest-order active input, ignoring all other active inputs.

Additional Information

• The successive approximation A/D converter has a shorter conversion time compared to the counter ramp A/D converter.
• Counter type ADC and successive approximate ADC use DAC Counter type ADC uses linear search and successive approximation type ADC uses binary search
• A ring counter is used in successive approximation-type ADC
•  Dual slope ADC is the most accurate

Concept:

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.

Concept:

• 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.

Resolution for n – bit A/D converter  will be:

\(R= \frac{V_{FS} \ \times \ (2^ib^i)}{{{2^n} - 1}}\)

Where 

R = Resolution

VFS is reference voltage 'or' Full-scale voltage

n = number of bits

2ⁱbⁱ gives output voltage value.

Calculation:

Given:

V_FS = 5.8 V

n = 4

R = 05 V

\( 5= \frac{5.8 \ \times \ 2^ib^i}{{{2^{4}} - 1}}\)

\( 2^ib^i= \frac{5 \ \times \ 15}{{5.8}}\)

2ibi = 12.93 V ≈ 12 V

In bits, the output voltage will be 1100

Hence option (1) is the correct answer.

Important Points

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:

\( R= \frac{{{V_{FS}}}}{{{2^N} - 1}}\)

No. of levels = 2N – 1

Vr is reference voltage 'or' Full-scale voltage

Concept:

• 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:

\( R= \frac{{{V_{FS}}}}{{{2^N} - 1}}\)

No. of levels = 2N – 1

Vr is reference voltage 'or' Full-scale voltage

Resolution for n – bit A/D converter in percentage will be:

\(= \frac{V_{FS}}{{{2^n} - 1}} \times 100\)

Calculation:

Given: n = 10, VFS = 10.23 V

\( = \frac{10.23}{{{2^{10}} - 1}}\)

= 10 mV

Counter type ADC:

• Counter-type ADC is very simple to understand and also easy to operate.
• Counter-type ADC design is less complex, so the cost is also less.
• ·Speed is less, since each time the counter has to begin from ZERO.
• There may be conflicts if the next input is sampled before the completion of one process.
• In a Counter type ADC, the conversion time varies.

IMPORTANT POINTS:

Comparison (best to worst)

Resolution:

Resolution of ADC is a change in analog voltage corresponding to a 1-bit increment.

Resolution is the number of bits per conversion cycle that the converter is capable of processing.

\(R=\frac{V_{range}}{2^n}\)

n = No. of bits of ADC

V_range = V_max - V_min

Analog output = Reslotion x Decimal equivalent to binary

V_o = R x D

Calculation:

V_range = V_max - V_min

V_max = 2.56 V

V_min = 0 V

⇒ V_range = 2.56 V

n = 8

Resolution is

\(R=\frac{V_{range}}{2^n}\)

⇒ \(R=\frac{2.56}{2^8}\)

∴ R = 0.01.

Output voltage V_o = 1 V

⇒ 1 = 0.01 x D

∴ D = 100

The binary value of 100 is

The binary equivalent of 100 is (011 001 00)₂

Concept:

Flash Type ADC:

1) It is the fastest ADC among all the ADC types.

2) An n-bit flash type ADC requires:

2n -1 comparators, 2n resistors and one 2n × n priority encoder. 

Calculation:

The number of comparators required to build an 8-bit flash ADC will be:

N = 2⁸ - 1

N = 256 - 1

N = 255

Dual slope ADC:

• These reduce design complexity and improves measurement quality.
• Dual-Slope integration type ADC is the most accurate type of ADC because of non-dependency on variation in components values caused by noise.
• It is quite slow in nature and used in application as digital voltmeter, multimeters etc.
• In dual slope and single slope ADCs instead of using a DAC with a ramped output, we use an op-amp circuit called integrator to generate a sawtooth wave.
• These are used in the precision application.

• Counter type ADC and successive approximate ADC uses DAC
• Counter type ADC uses linear search and successive approximation type ADC uses binary search
• A 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