16

What is resolution
of the 4 – bit DAC?


% Resolution = 1 /
( 2^{N} – 1)
Where N =
Number of bit
Therefore resolution of the 4 – bit DAC is
% Resolution = 1 / ( 2^{4} – 1)
= 1 / 15
= 6.67%

17

A 4 – bit DAC has a
step size of 10 mV. What is output voltage and Percentage resolution?


A 4 – bit DAC has 15 ( 2^{4} – 1 )
steps of 10 mV. Therefore the full scale output is equal to 0.15 V ( 15 × 10 mV ). The percentage
resolution is ( 10 mV / 0.15 ) × 100 =
6.67%

18

A 4 – bit DAC has
output voltage of 0.10 V for digital input of 0101. What is full scale
output?


The full scale output of the DAC is equal to
product of step size and number of steps.
Full
scale output = 0.10 V ( 2^{4} – 1)
= 1.5 V

19

Explain the term :
Unipolar DAC and Bi – polar DAC


Unipolar DAC
 It is a DAC in
which the binary input is an unsigned number and the output is a positive
voltage or current.
Bi polar DAC
 It is a DAC in
which the binary input is a signed number and the output is a either positive
or negative value.

20

What is reason
behind the name ‘ R – 2R ladder type DAC ’?


The R – 2R ladder type DAC consists of
series parallel combination of two resistors R and 2R therefore it is known
as the R – 2R ladder type DAC.

21

Why high impedance
circuit is used at the output of the R – 2R ladder type DAC?


To prevent loading

21

Write only the name
of different types of DAC.


Different types of
DAC
 R – 2R Ladder
type DAC
 Weighted
resistor type DAC
 Switched
current source type DAC
 Switched
capacitor type DAC

22

Which is the most
popular DAC?


The R – 2R type DAC

23

Which is the
simplest type ADC?


Counter

24

Which is the fastest
type ADC?


Flash or parallel or simultaneous

25

Which is the Slowest
type ADC?


Dual slope

26

By which factor the
input of the weighted resistor DAC is amplify?


The input of the Weighted resistor DAC is
amplified by the ratio of the feedback resistor to the input resistor.

27

Describe the
disadvantage of the weighted resistor type DAC.


Disadvantage
 There must be each
bit position of the digital input for different value of precision resistor.

28

What are the
different types of the switched type voltage source DACs? Why it is called as
switched type voltage source DACs?


Voltage Source DACs
 R – 2R type DAC
 Weighted Resistor
Switched Type Voltage Source DAC
 When an input position
goes high, the output high voltage switched in the circuit which is summed to
other input voltages, therefore it is called as switched type voltage source
DAC.

29

What is advantage of
the current source type DACs over the voltage source type DACs?


The switching in and out of the current type
DACs is faster than the voltage source type DACs.

30

Give reason ‘ The
switched current type DAC is sometime called as multiplying DAC.’


When the output of the switched current type
DAC is product of digital input and analog reference voltage, it is called as
multiplying DAC.

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