There is provided an operational amplifier capable of detecting that an input terminal has been open circuited without restricting the voltage range of an input signal. The operational amplifier includes a first comparator which detects that an inverting input terminal of an operational amplifier has been open circuited, a second comparator which detects that a non-inverting input terminal of the operational amplifier has been open circuited, a first resistor and a first switch which are controlled by output signals of the first comparator and the second comparator and which are connected in series between the non-inverting input terminal and a ground terminal of the operational amplifier, and a second resistor and a second switch which are connected in series between the inverting input terminal and a supply terminal of the operational amplifier.