A-D and D-A Converters - PracticePaper

Please wait while the activity loads.
If this activity does not load, try refreshing your browser. Also, this page requires javascript. Please visit using a browser with javascript enabled.

If loading fails, click here to try again

Question 1

An 8-bit ADC converts analog voltage in the range of 0 to

+5 \mathrm{~V}

to the corresponding digital code as per the conversion characteristics shown in figure. For

\mathrm{V}_{\text {in }}=1,9922 \mathrm{~V}

, which of the following digital output, given in hex is true?

A	$64 \mathrm{H}$
B	$65 \mathrm{H}$
C	$66 \mathrm{H}$
D	$67 \mathrm{H}$

GATE EE 2023 Digital Electronics

Question 1 Explanation:

Resolution

=\frac{V_{F S}}{2^{n}-1}=\frac{5}{2^{8}-1}=0.0196 \mathrm{~V}

Now, No. of step

=\frac{\mathrm{V}_{\text {in }}}{\text { Resolution }}

=\frac{1.9922}{0.0196}=(101.64)_{10}

For

(101)_{10}

the analog input is less than

1.9922 \mathrm{~V}

.
So, here we take

(102)_{10}

\therefore \quad(102)_{10}=66 \mathrm{H}

Question 2

A 2-bit flash Analog to Digital Converter (ADC) is given below. The input is

0 \leq V_{IN} \leq 3

Volts. The expression for the LSB of the output

B_0

as a Boolean function of

X_{2},X_{1} \; and \; X_{0}

A	$X_{0}[\overline{X_{2}\oplus X_{1}}]$
B	$\bar{X_{0}}[\overline{X_{2}\oplus X_{1}}]$
C	$X_{0}[{X_{2}\oplus X_{1}}]$
D	$\bar{X_{0}}[X_{2}\oplus X_{1}]$

GATE EE 2016-SET-1 Digital Electronics

Question 2 Explanation:

The input to digital circuuit is

X_2,X_1,X_0

and output is

B_1,B_0

B_0=\bar{X_2}\bar{X_1}X_0+X_2X_1X_0

\;\;=X_0(\bar{X_2}\bar{X_1}+X_2X_1)

\;\;=X_0(\overline{X_2\oplus X_1})

Question 3

A temperature in the range of -40

^{\circ}

C to 55

^{\circ}

C is to be measured with a resolution of 0.1

^{\circ}

C. The minimum number of ADC bits required to get a matching dynamic range of the temperature sensor is

A	8
B	10
C	12
D	14

GATE EE 2016-SET-1 Digital Electronics

Question 3 Explanation:

Temperature range of

-40^{\circ}C \; to \; 55^{\circ}C

So. Total range in

95^{\circ}C

Since, resolution is

0.1^{\circ}C

So, number of steps will be 950
To have 950 steps, we need at least 10 bits.

Question 4

An 8-bit, unipolar Successive Approximation Register type ADC is used to convert 3.5 V to digital equivalent output. The reference voltage is +5 V. The output of the ADC, at the end of 3rd clock pulse after the start of conversion, is

A	1010 0000
B	1000 0000
C	0000 0001
D	1000 0000

GATE EE 2015-SET-1 Digital Electronics

Question 4 Explanation:

The reference voltage is 5 V.
The number of bits in ADC are 8.
So, the resolution will be

=\frac{5}{2^8-1}=\frac{5}{255}

The applied input is 3.5 V.
The succesive approximation ADC start working from the MSB so,

After one clock:
SAR will toggle it's MSB from

0\rightarrow 1

. So, output of SAR will be 1000 0000.

After second clock:
SAR will toggle its 7th bit from

0\rightarrow 1

but 1100 0000 will result in value greater than 3.5. So, output of SAR after 2nd clock will be 1000 0000.

After third clock:
SAR will toggle it's 6th bit from

0\rightarrow 1

and output will be 1010 0000.

Question 5

The Octal equivalent of HEX and number AB.CD is

A	253.314
B	253.632
C	526.314
D	526.632

GATE EE 2007 Digital Electronics

Question 5 Explanation:

Hex Number (AB.CD)

1010\;\;1011\;.\; 1100\;\;1101

For finding its octal number, we can add one zero in both extreme and grouping.

010\;101\;011\;.\;110\;011\;010

Its equavalent octal number is

(253.632)_8

There are 5 questions to complete.