ADC and DAC convertions

[Anonymous]

 Hi,

   

I am trying to input Analog signal, filter it and output back.

   

I have a big falt.

   

I opend an example project "Filter_ADC_VDAC Example Project" and tried to simulate it

   

I am geting a very noisy and deformated outputs (pics attached)

   

1. for 100Hz

   

2, 1.9 Khz

   

When I am anning an example project I understanding that there is any problem? eror? 

   

Do the DAC work with so terrible errors?

   

Maybe somebody tried it?

   

Thank

   

Piona

[ETRO_SSN583 · Accepted solution]

I simplified the project, at least for me, by eliminating all the AC coupling and bias stuff.

       

Note the the output waveform is ~ 5 db down at the 1.9 Khz corner freq per the filter wizard

   

plot. You can gain upo the filter to take care of that if you wish.

       

Regards, Dana.

                                   

[ETRO_SSN583]

Here is the same setup except WaveDAC81 generatinga  square wave

   

and filter taking out harmonics, leaving the fundamental sine -

       

[Anonymous]

 Thanks Dana!

   

I just didnt understood why the filter makes sin from square vawe?

[Anonymous]

 Can you please remake the project cannot open it

[Anonymous]

 I made one like yours 🙂 work.

   

Do you know what makes the phase shifting?

[ETRO_SSN583]

A square wave is an infinite series of odd harmonics of sinusoids. So

   

if we take out all the harmoincs but the fundamental, or just one harmonic,

   

any harmonic, we get a sinusoid.

       

In this case filter is taking out all harmonics starting with the first harmonic at 3.8 Khz.

   

So all that is left is a single sine, the fundamental sine, at 1.9 Khz.

       

We could have done this with BP filter also.

       

Here is a java example of changing the harmonic content of a squarewave - www.falstad.com/fourier/e-square.html

       

Regards, Dana.

[ETRO_SSN583]

Re phase shift -

       

www.tedpavlic.com/teaching/osu/ece209/lab3_opamp_FO/lab3_opamp_FO_phase_shift.pdf

       

Regards, Dana.