| 摘要 |
PROBLEM TO BE SOLVED: To improve ripple removal rate of a series regulator by reducing a ripple voltage appearing in an output voltage due to the variation of an input voltage in a normal operation after a stable output voltage is obtained posterior to the power supply. SOLUTION: When an external start voltage source starts its operation, bias currents are supplied from a transistor A4 to a reference voltage circuit 16, and a reference voltage is supplied form the reference voltage circuit 16 to an amplifier part 17. When the output voltage of a power transistor 13 increases, and the value of a divided voltage to be applied to the transistor A6 increases to the value of a fixed voltage applied to the transistor A5, the transistor A6 is turned on, and the transistor A5 is turned off. The supply of the bias currents is started from a transistor A10 to the reference voltage circuit 16. Simultaneously, a bias switching circuit 15 starts its operation, and the supply of the bias currents from the transistor A4 to the reference voltage circuit 16 is interrupted.
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