| 摘要 |
PROBLEM TO BE SOLVED: To provide a constant current circuit that is operable at low voltage, a power apparatus using it, and a light emitting device. SOLUTION: In the constant current circuit 100 that supplies a constant current Ic to a circuit connected to a current output terminal 102, a first transistor M1 is provided on the current path of the constant current Ic. The first transistor M1 and a gate terminal serving as a control terminal are commonly connected to a second transistor M2. A first current-to-voltage conversion part 14 converts a current Im2 flowing in the second transistor M2 into a voltage. A constant current source 10 generates a reference current Iref. A second current-to-voltage conversion part 16 converts the reference current into a voltage. Voltages Vx1, Vx2 are inputted to a first error amplifier 12 to regulate the gate voltages of the first and second transistors M1, M2. A voltage regulating part 20 regulates the voltage at the gate terminal of a third transistor so that the voltage at one end of the second transistor M2 approaches a predetermined reference voltage. COPYRIGHT: (C)2006,JPO&NCIPI
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