I am a mechanical engineer who is new to direct digital synthesis. I am trying to recreate the attenuation circuit to adapt the EVAL-AD5933 for measurements of small impedance (see image included) from page 30 of the EVAL-AD5933 data sheet.
I have recreated the circuit, but am not sure about the source of VDD (circled in the image). The data sheet describes it as a system setting of 3.3V. My question is whether the VDD source circled in the image is from an external voltage source or pulled from the EVAL board? If it is pulled from the EVAL board, how is this done?