US Patent 7928708 Constant-voltage power circuit

A differential amplifier receives a reference voltage and a divided voltage dividing an output voltage, and outputs a control voltage in accordance with the difference between the reference voltage and the divided voltage. The control voltage output from the differential amplifier is supplied to an output amplifier. The output amplifier generates a stabilized output voltage from a high-potential-side power supply voltage in accordance with the control voltage. A P-type MOS transistor is connected to a node of the output voltage, and the MOS transistor carries a current from the node of the output voltage. A current control circuit controls a gate of the P-type MOS transistor so that the current flowing through the P-type MOS transistor becomes a constant value.