| 摘要 |
PROBLEM TO BE SOLVED: To provide a constant current circuit and a constant voltage circuit for simultaneously providing a reference voltage and a reference current. SOLUTION: An output Vref of a reference voltage generating circuit 100 is input to the (-) input terminal of an operational amplifier 102; an output voltage Vout of a reference voltage trimming circuit 103 whose total resistance value is not changed with trimming is input to the (+) input terminal of the operational amplifier 102 and both voltage values are compared. An output of the operational amplifier 102 controls the gate of an output transistor 104 so as to virtually short-circuit two inputs of the operational amplifier 102 to set an output voltage Vref1 at a desired value. If the output voltage Vref1 needs to be adjusted, resistors R1, R2 are trimmed. Since the total resistance value is not changed with the trimming, both the constant voltage and the constant current can be stably obtained. COPYRIGHT: (C)2009,JPO&INPIT
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