Every ground is tied to the same ground. The Op Amp is ADA4000-2 from Analog device.
I created a DAC signal that goes up/down from 1.55V. As you see the yellow signal (channel 1), this 1.55V is like a DC-Offset. The blue signal (channel 2) is the Vout pin, the output of the Op Amp.
If you take a close look at the part where the values are lower than 1.55V from channel 1, I was expecting the same decreasing pattern from channel 2. However, that part is constant to 4.1V and I think the output becomes saturated.
I cannot understand this reason. What seems to be the reason for this constant output? I wanted a unity gain, but I cannot find the reason for this. Appreciate your help.