CURRENT OUTPUT CIRCUIT FOR TEMPERATURE AND HUMIDITY DETECTOR, TEMPERATURE AND HUMIDITY DETECTOR PROVIDED WITH THIS CURRENT OUTPUT CIRCUIT

摘要

PROBLEM TO BE SOLVED: To suppress the heating value of a transistor by providing an applied voltage regulating circuit for changing the voltage applied to a constant current circuit according to the power consumption in the constant current circuit containing the transistor for controlling output direct current and an arithmetic amplifier. ;SOLUTION: As the applied voltage regulating circuit, a step-down chopper circuit 2 which is a switching power source circuit and a differential amplifier are used. To a load resistance RL, a prescribed output current Io (Io=Vi/Rc) is carried by the action of the differential amplifier, a transistor Tr, and a current detecting resistance Rc. Vi is the voltage signal of temperature or humidity. The voltage added between collector emitters of the transistor Tr (V2-V1) is detected the differential amplifier, and the step-down chopper circuit 2 is controlled so as to make it constant, whereby the voltage can be stepped down from Vc to V4 (V4=V2+RL.Io). Consequently, the voltage in a point A can be reduced, and the heating value of the transistor Tr can be suppressed in its turn.;COPYRIGHT: (C)1998,JPO