Patent ID: 8558590

Claim:
A reference current generating circuit comprising: a reference voltage generating unit that generates a reference voltage; a bias voltage generating unit that includes a first transistor of a first conductive type and a second transistor of a second conductive type that each output a reference current based on the reference voltage and generate a first bias voltage and a second bias voltage, respectively; a first output transistor of a first conductive type that outputs a current corresponding to a reference current when the first bias voltage is supplied to a control terminal of the first output transistor: a second output transistor of a second conductive type that outputs a current corresponding to a reference current when the second bias voltage is supplied to a control terminal of the second output transistor; an input-output unit in which one terminal thereof is connected between an output terminal of the first output transistor and an input terminal of the second output transistor and the other terminal is connected to a load circuit, the input-output unit supplying current from the first output transistor to the load circuit or supplying current from the load circuit to the second output transistor; and a switching control unit that outputs a control signal to the input-output unit to turn on or off the first output transistor and the second output transistor based on voltage of an output from the input-output unit, wherein the switching control unit includes: a saturation voltage generating circuit that generates a first reference voltage that serves as a boundary between a saturation region of the first transistor and a non-saturation region of the first transistor, and generates a second reference voltage that serves as a boundary between a saturation region of the second transistor and a non-saturation region of the second transistor, based on the first bias voltage and the second bias voltage; a first comparator that compares the output voltage of the input-output unit and the first reference voltage; a second comparator that compares the output voltage of the input-output unit and the second reference voltage; and a state machine that switches a connection condition of a first switching element of the input-output unit and a second switching element of the input-output unit based on a result of comparison by the first comparator and the second comparator.