| 摘要 |
PROBLEM TO BE SOLVED: To prevent a field effect transistor 31 from intermittently operating. SOLUTION: When a decision is made that a PTC thermistor 34 is in temperature protection state for controlling the change in gate-source voltage, a CPU 43 outputs a stop signal to a switch 45 and opens the output terminal 42c of an operational amplifier 42 and the output terminal 41b of an electronic controller 40. Output of the output voltage Vo from the operational amplifier 42 to the gate terminal of the field effect transistor 31 is thereby stopped. Consequently, the stop state of the field effect transistor 31 can be maintained even if the temperature of the field effect transistor 31 drops and the resistance R1 of the PTC thermistor 34 decreases, and stress in the field effect transistor 31 is prevented from being accumulated. COPYRIGHT: (C)2010,JPO&INPIT
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