| 摘要 |
PROBLEM TO BE SOLVED: To provide a series regulator power source circuit to suppress or reduce cost up of a system, with high stability in operation and high performance. SOLUTION: This power source circuit is constituted by providing a buffer circuit 6 in which difference between the maximum outputted voltage and inputted voltage VIN of an operational amplifier circuit 1 is within 0.3 V and outputted resistance becomes low at an output stage in the operational amplifier circuit 1 to input reference voltage Vref from a reference voltage circuit 2 and voltage obtained by dividing outputted voltage VOUT from a voltage dividing circuit 3, to control an output control transistor MO of a PMOS-FET (P channel metal oxide semiconductor field effect transistor) by an output signal and to output the stabilized outputted voltage VOUT to an output terminal 5. Thus, operation at low voltage is enabled, the operation is stabilized and use of an output capacitor C with small capacitance is enabled.
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