25 March 2020

Analog To Digital & Digital To Analog Interview Question Answer - 3


31
How the switching of the capacitor is done in the switched Capacitor type DAC?


Switched Capacitor Type DAC

  • The switching of the capacitor is done by two phase clock in the switched capacitor type DAC. 
  • When the phase Ø1 is at high state, all the capacitors are switched to ground and discharged. 
  •  Similarly when the phase Ø2 is at high state, all the capacitors are switched to reference voltage.

32
Write the general formula for the output voltage of the switched Capacitor type DAC.


The output voltage of the switched capacitor type DAC
   Vout =  ( Ceq / 2C ) × E
   Where Ceq   =  Equivalent capacitance when all the inputs are
                            high
    C    =  Sum of the all capacitance in the circuit
    E  =  Reference voltage

33
What are the applications of the switched capacitor type DAC?


The switched capacitor type DAC is used to construct filters and amplifiers.

34
Why the counter type ADC is called as digital ramp ADC?


The counter type ADC is called as digital ramp ADC because the output of the DAC is staircase or step by step.

35
Which are the digital devices used for the construction of the counter type ADC?


AND gate, latches and Digital to Analog converter

36
How to calculate resolution of the analog to digital converter?


The resolution of the analog to digital converter is given by the ratio of full scale reading to the number of bits in the counter.
  • Resolution = Full scale reading / Number of bits


37
What are the disadvantages of the counter type A / D converter?


Disadvantages
  • The conversion time depends upon the analog input therefore more conversion time for the larger input.


38
Explain the term : Quantization error


Quantization error
  • The resolution of the counter type analog to digital converter has built in error, it is referred as quantization error.


39
Why the counter type A / D converter is very slow?


The counter type A / D converter is very slow because it reset after each conversion.

40
Why the tracking type A / D converter is faster than the counter type A / D converter?


The count in the tracking type A / D converter is not reset after each sample therefore it is faster than the counter type A / D converter.

41
What is disadvantage of tracking type A / D converter?


Disadvantage of tracking type A / D converter
  • When the analog input remains constant, the output of the counter oscillates about the constant analog input.


42
Define : Conversion time


Conversion time
  • It is defined as the time required for converting a single analog input to digital output.


43
What are the advantages and disadvantages of the flash type A / D converter?


Advantage of flash type A / D converter
  • Less conversion time

Disadvantage of flash type A / D converter
  • More number of comparators requires i.e. it requires 2N – 1 comparators for N bit converter


44
How many comparators do the flash type A / D converter requires?


The n bit flash type A / D converter requires 2n – 1 comparators.

45
Why the flash type A / D converter do not require clock signal?


The flash type A / D converter don’t require clock signal because there is no timing period in this type of converter.


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