I am working on a card that utilizes an AD598AD. I have found that the relationship between the resistance set between level 1 and level 2 and the amplitude of the excitation output does not follow the diagram in the specification and I get consistently lower excitations. This seems mostly due to a low pass filter installed in the level setting loop. It appears this filter was installed due to recommendation from Analog devices in order to clean up excitation distortion due to the chip being used in a multi layered board. I am having trouble characterizing how this filter impacts the excitation amplitude, and was hoping for some insight into this or how the excitation circuit functions. Currently all attempts I have made to model the circuit have not yielded the results I am experiencing.
