written 5.7 years ago by |
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
resolution=$\frac{V_{Fs}}{2^{n-1}}$
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
Accuracy=$\frac{V_{FS}}{2(2^{n-1})}$
$\frac{10.2}{2\times 25.5}$=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.