Electronics and Communication Engineering - Digital Electronics - Discussion

18. 

An 8 bit DAC has a full scale output of 2 mA and full scale error of ± 0.5%. If input is 10000000 the range of outputs is

[A]. 994 to 1014 μA
[B]. 990 to 1020 μA
[C]. 800 to 1200 μA
[D]. none of the above

Answer: Option A

Explanation:

10000000 = 128, 11111111 = 255

If there is no error, output = = 1004μA.

Maximum error =

Hence range of output 994 to 1014 μA.


Renuka said: (Sep 25, 2014)  
2000 mentioned above indicates ?

Sudha said: (Feb 23, 2015)  
2 mA in μA.

Sharon said: (Mar 12, 2015)  
Please give me clear explanation of above expression.

Adi said: (Sep 5, 2016)  
Please give me the formula to be used here.

Teju said: (Feb 10, 2017)  
8bit DAC.

Step size= Full scale/number of steps.
Number of steps =255.
=2ma/255=7.84m.

Ideal output to input = step size*input range.
7.84 * 128 = 1004 Ma.
Error = 0.5%*input range.
=0.5%*2ma = 10ma.

Prakash Kumar Saini said: (Mar 13, 2018)  
The step size is 2mA/255 = 7.84 μA. Since 10000000 = 12810, the ideal
output should be 128 * 7.84 μA. The error can be as much as
0.5% * 2mA = 10μA.

Thus, the actual output can deviate by this amount from the ideal,
1004μA , so the actual output can be anywhere from 994 to 1014 μA.

Priyadarshini said: (Jul 30, 2018)  
How 128 as the input range here?

A.R.Poomalai said: (Sep 29, 2018)  
@Priyadarshini.

Convert this binary 10000000 to decimal you will get 128.

Sujith K said: (Aug 15, 2019)  
But How this number of steps becomes 255, why not 256?
So, 2^8=256.

Akshit Jain said: (Apr 19, 2020)  
@Sujith K.

Here we are considering maximum 8 bit number for the max range.

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