Nice to meet you by email. I am Sophia, a FAE from China. My customer had a damage issue with LM224. The schematic of LM224 is as below. Customer used 3 pieces of LM224 to sense current of A、B and C three-phase separately. As shown below, the LM224(integrating the below 4 amplifiers) is used to sense phase-A current. The input current of the first amplifier is 1mA and the output voltage of it should be 1.2V. The second amplifier is used as second-order filter. The third amplifier is used as rectifier and the amplification of the forth amplifier is 1.3. The abnormal phenomenon is when equipment is running, the output voltage of the first amplifier is always +15V, whether there is input signal or not. This abnormal phenomenon happened for phase A、B and C current sensing at the same time. And the current sensing schematics of A、B and C are same. Failure ratio is 2/40. Do you have any suggestions about the issue?