1
GATE ECE 2016 Set 2
MCQ (Single Correct Answer)
+2
-0.6
In an N bit flash ADC, the analog voltage is fed simultaneously to 2N− 1 comparators. The output of the comparators is then encoded to a binary format using digital circuits. Assume that the analog voltage source Vin(whose output is being converted to digital format) has a source resistance of 75 Ω as shown in the circuit diagram below and the input capacitance of each comparator is 8 pF. The input must settle to an accuracy of 1/2 LSB even for a full scale input change for properconversion. Assume that the time taken by the thermometer to binary encoder is negligible. If the flash ADC has 8 bit resolution, which one of the following alternatives is closest to the maximum sampling rate?
A
1 megasamples per second
B
6 megasamples per second
C
64 megasamples per second
D
256 megasamples per second
2
GATE ECE 2008
MCQ (Single Correct Answer)
+2
-0.6
In the following circuit, the comparator output is logic “I” if V1 > V2 and is logic “0” otherwise. The D/A conversion is done as per the relation $${V_{DAC}} = \sum\limits_{n = 0}^3 {{2^{n - 1}}{b_n}\,\,} Volts,$$$where b3(MSB), b2, b1 and b0 (LSB) are the counter outputs. The counter starts from the clear state. The magnitude of the error between VDAC and Vin at steady state in volts is A 0.2 B 0.3 C 0.5 D 1 3 GATE ECE 2008 MCQ (Single Correct Answer) +2 -0.6 In the following circuit, the comparator output is logic “I” if V1 > V2 and is logic “0” otherwise. The D/A conversion is done as per the relation $${V_{DAC}} = \sum\limits_{n = 0}^3 {{2^{n - 1}}{b_n}\,\,} Volts,$$$ where b3(MSB), b2, b1 and b0 (LSB) are the counter outputs.

The counter starts from the clear state.

The stable reading of the LED display is

A
06
B
07
C
12
D
13
4
GATE ECE 2007
MCQ (Single Correct Answer)
+2
-0.6
In the digital-to-Analog converter circuit shown in the figure below,
$${V_{R\,}}\, = \,10V$$ and $$R\, = \,10k\Omega$$

The current i is

A
$$31.25\,\mu {\rm A}$$
B
$$62.5\,\mu {\rm A}$$
C
$$125\,\mu {\rm A}$$
D
$$250\,\mu {\rm A}$$
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