AD9739: Output amplitude DC-offset

Document created by analog-archivist Employee on Feb 23, 2016Last modified by analog-archivist Employee on Feb 23, 2016
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Why is the difference in DC-offset so large between devices? How to avoid?

 

The DC offset is a result of the balun, MABACT0039, only providing a DC short
to the IN pin while the IP pin is connected to a 50 ohm load (as well as 90.9
ohm resistor). 
We now recommend using a balun (see attached) that has an extra tertiary
winding that provides DC short such that both IP and IN remain at 0 V bias. 
Note,a balun (or transformer) has a lower cut-off frequency hence should only
be used for ac applications where reconstructed signal falls within its 1 dB
passband.
I also attached some more information on the output stage of the AD9739 below.

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