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Error of ADI Inc.??? When applying the RF Transformer in DAC

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indeed

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Merry Christmas everybody,

I am facing a tough problem, which has been boring me for a few days.
That is about a current output DAC, and how to disign the matching circuit.

AD9755 is a complementary current output DAC.
The full scale of each output channel is 20mA.
When applying AC couple, ADI suggests transformer, but the reference design using a 1:1 transformer seems wrong.

Below is quoted from AD9755 DataSheet.
"An RF transformer such as the Mini-Circuits T1–1T provides excellent rejection of common-mode distortion (i.e., even-order harmonics) and noise over a wide frequency range. When IOUTA and IOUTB are terminated to ground with 50 ohm, this configuration provides 0 dBm power to a 50 ohm load on the secondary with a DAC fullscale current of 20 mA."

But I think the power tranfers to the 50ohm load is 4.4mW, that is 6.47dbm.

I also present my simulation result from multisim7.


Another question is about the matching circuit, how to choose the proper value of relative resistors?

Very eager to have someone help me!!

Thanks!!
 

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