Performance Parameters of DAC
1 Answer

1) Resolution :-

Resoluiton of a DAC can be defined in two different ways:-

i) Resolution is the no. of different analog o/p voltagae values that can be provided by a DAC. For a n-bit DAC

Resolution =$2^{n}$

Hence the resolution of a 4-bit DAC is $2^{4}=16$ and that of a 3-bit DAC is $2^{3}=8$.

Hence resolution increases with the increase in no.of bits.

ii) Resolution is defined as the ratio of change in anlog o/p voltage resulting from a change of 1 LSB at the digital i/p. For an n-bit the


Where $V_{Fs}$= Full scale o/p voltage

=o/p voltage corresponding to the digital i/p with all digits 1

Resolution can be treated as the smallest change in the analog o/p voltage. Resolution will improve with reduction in the smallest change in the o/p voltage

2) Accuracy:- It is a comparison of actual o/p voltage with expected o/p. It is expressed in percentage ideally, the accuracy of a DAC should be, at nor st +1/2 of its LSB. If the full scale o/p voltage is 10.2 v then for an 8-bit DAC accuracy can be given as


$\frac{10.2}{2\times 25.5}$=20mv

3) Linearity:-

The relation between the digital i/p and analog o/p should be linear. Practically it is not so due to the error in the values of resistars used for the resistive networks

4) Setting time:-

The time required to settle the analog o/p with in 1/2 LSB of the final value, after the change in digital i/p is called a settling time.

5)Conversion time:-

It is a time required for conversion of analog signal into its equivalent. It is also called as settling time. It depends on the response time of the switches and the o/p of the amplr.

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