8 Replies Latest reply on Jul 6, 2015 5:05 AM by DaKn_263916

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

• ###### 2. Re: ADC and DAC convertions

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.

• ###### 3. Re: ADC and DAC convertions

Here is the same setup except WaveDAC81 generatinga  square wave

and filter taking out harmonics, leaving the fundamental sine -

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• ###### 4. Re: ADC and DAC convertions

Thanks Dana!

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

• ###### 5. Re: ADC and DAC convertions

Can you please remake the project cannot open it

• ###### 6. Re: ADC and DAC convertions

I made one like yours :) work.

Do you know what makes the phase shifting?

• ###### 7. Re: ADC and DAC convertions

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.

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• ###### 8. Re: ADC and DAC convertions

Re phase shift -

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

Regards, Dana.

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