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AD9834 LC Filter

Question asked by flz47655 on Dec 18, 2012
Latest reply on Dec 18, 2012 by flz47655

What impedance should have an LC filter connected to IOUT pin of AD9834?

 

I have a low pass chebyshev filter with a cutoff frequency of 32.5 MHz with 50 ohm impedance designed with http://www.wa4dsy.net/filter/hp_lp_filter.html and built with commercial values

http://img834.imageshack.us/img834/4868/filtrolc.png

Signal without filter is without biasing:

http://imageshack.us/a/img221/723/3mhzdopodds.th.png

But with filter attached signal is distorting.. In image yellow is signal DDS_OUT and blue is DDS_OUT_FILT

http://imageshack.us/a/img600/8315/3mhzprimadopofiltro.th.png

There is a lot of offset, vertical offset of track is shifted to show both tracks.

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