I'm using the ADA4666-2 to operate as the error amplifier in a constant current/constant voltage feedback loop. The constant current loop has adjustable gain.
However, I don't get the expected voltage at pin 3 of the ADA4666-2. After I removed R29 and R30, leaving the +INA pin open circuit, I only measure 57 kohm to ground (the V- pin). The datasheet says it should be > 10 Gohm. I have five prototype PCBs, and they all show this. Is it possible the ADA4666-2's were damaged during assembly? I'm powering the system with 12V, single ended, that seems to be very safe, and the maximum voltage applied to pin 3 is 1.25V. When powered on, though, it never gets higher than 1.0V.
Any idea what went wrong?