Thank you very much for your help.
I want to protect the circuit from the voltage applied to the output when VCC is not supplied to the OPA172.
Can you tell me the appropriate circuit configuration?
In normal operation, 12v is supplied to the vcc of the opA172, but when the main power supply fails and 12v is not supplied, the configuration is to use an external sub-battery to drive the emergency alarm circuit.
The sub-battery is assumed to be a coin cell battery such as cr2032.
In this case, the opa172 will be irrelevant, but 3v will be applied to the output line.
We want to make sure that the opa172 can be used without damage when the main power supply is restored.
By the way, I made some measurements with the evaluation board I created.
When there was no VCC, about 42mA was flowing from the sub-battery.
When I disconnected the output line of the OPA172, it dropped to about 3mA, which is the current consumption of the emergency alarm circuit.
Can you tell me about this phenomenon as well?
This may be a basic question about op-amps, but please help me.