Abstract: A temperature detecting device comprises a semiconductor diode temperature sensor having a resistance characteristic which varies with variations in temperature, and a constant current circuit connected in series. A power source is connected in parallel with the series circuit and connected in parallel with a constant voltage circuit. A resistance ladder circuit is connected between an output terminal of the constant voltage circuit and one terminal of the power source, and an output terminal of the resistance ladder circuit is connected to a first input terminal of a differential amplifier. A second input terminal of the differential amplifier is connected to a connection point of the semiconductor diode and the constant current circuit.

Abstract: A constant current circuit comprising first and second insulated gate field effect transistors connected in series, and third and fourth insulated gate field effect transistors connected in series. The series connected transistor pairs are connected in parallel. The first and third transistors have different threshold voltages, and have their respective gate electrodes connected together, and the second and fourth transistors have equal threshold voltages and have their respective gate electrodes connected together. The gate of the second transistor is connected to the node between the first and second transistors, and the gate of the third transistor is connected to the node between the third and fourth transistors.