An input circuit that detects an abnormality of a voltage generation of the input circuit. The circuit includes an external output terminal, an analog voltage generator. The generator includes a power supply terminal, a grounding terminal, and an internal output terminal. The circuit includes a first resistor, which is connected to the power supply and to the power supply terminal, a second resistor, which is connected to the ground and to the grounding terminal, a third resistor, which is connected to the internal output terminal and to the external output terminal, and a fourth resistor, which is connected to the node of the third resistor and the external output terminal and to the ground. When the grounding terminal or the power supply terminal is open, the analog voltage of the external output terminal is in an upper limit fail voltage range or in a lower limit fail voltage range.