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AD797 active filter

Question asked by Jinkyu_Park on Oct 20, 2016
Latest reply on Oct 21, 2016 by Jinkyu_Park

Hi all,

 

I designed an active low-pass filter by using AD797 and analog filter wizard as http://www.analog.com/designtools/en/filterwizard/Share?id=1865 . I expected that this filter will suppress the harmonic signal from a function generator. Normally, a function generator has the harmonic over then -70dB. The datasheet of AD797 has 100 or 120dB THD. So, I use it for my active low-pass filter.

 

My function generator has -75dB second harmonic and -85dB third harmonic. After I assembled the evaluation board as EVAL-FW-MOTHER and EVAL-FW-LPSK1. I checked the filter did not suppress the harmonic signals and increased about 2dB. I wondering this is normal or abnormal working of AD797?

 

And I need one single tone signal which has harmonic under -100dB. Would I get the recommendation or direction to get it?

 

Thank you.

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