I try to estimate the noise of my system, which use an AD9106 as a high frequency voltage source.
The value in the datasheet is -167dBm/sqrt(Hz) I tried to convert it in nV/sqrt(Hz) to get 1nV/sqrt(Hz).
It seems quite low to me yet not impossible. Also the output is a current should I convert the noise in current ? I would expect the noise to depend on the resistance used to convert in voltage.
Another question : would it be possible to use the outputs of the DDS directly to drive the inputs of a differential amp ? (please refer to the schematic attached)
In the evaluation board, there are 250ohms resistors used to convert the current in voltage then a differential amplifier. However, it forces to use larger resistors for the input of the OPA to not affect the current to voltage resistors, that increases noise.