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# proteus dac

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#### liewchin

##### Newbie
hi someone who is experts in proteus can help ?
I have set my power in configure power rails which are , Vcc =15V, VEE=-15V, Vref=5V
The schematic diagram would be something similar shown as below. i don't know what wrong ,why I get a 13.5 V at full scale . please help me ,I'm a beginner of using proteus .

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Hi,

What value do you expect?

Did you use voltmeters in your simulation to trace the signal from beginning to end?

Klaus

Hi,

What value do you expect?

Did you use voltmeters in your simulation to trace the signal from beginning to end?

Klaus
Hi klaus , i expect to get a value of 4.99V when the input number is 11111111.
yes , I'm using a dc voltmeter

Hi,

You have a simulation tool, so use it to debug your circuit:
* what is I14?
* what is Iout?
Of the DAC.

Klaus

Hi,

You have a simulation tool, so use it to debug your circuit:
* what is I14?
* what is Iout?
Of the DAC.

Klaus
hi , i got 4mA at I14 but it supposed be 1mA

and the iout is 1.35e-7 also not same with the calculation

Hi,

I doubt that "Iout - of the DAC" is that close to zero.

I14: just go on debugging straight forward. The current should be determined by R1. So what are the voltages at both sides of R1 wrtg?

Klaus

Hi,

I doubt that "Iout - of the DAC" is that close to zero.

I14: just go on debugging straight forward. The current should be determined by R1. So what are the voltages at both sides of R1 wrtg?

Klaus

not sure , but is it this what you mean ?

View attachment 175243
not sure , but is it this what you mean ?

Hi klaus,

i just realised i will get the same answer with theoretical calculation if I divide by 2 . but I dunnoe why divide by two .Thanks in advanced

Hi,

When thereis +5V at one pin and -5V at the other pin, then it's 10V in total across the resistor.
Divided by 5kOhms this gives 2mA.

I can't see why there is -5V at Pin 14.

--> a guess a simulation (library) error.
But I didn't go deep into the datasheet.

Do you have a real circuit to verify against?

Klaus

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