1. Field of the Invention
The present invention relates to a constant-voltage power circuit, which supplies a stable voltage with respect to transient variations of a load current.
2. Description of the Related Art
A linear regulator circuit is a so-called constant-voltage power circuit. The linear regulator circuit is largely classified into two; namely, it is composed of a differential amplifier and an output amplifier. In a low drop-out type linear regulator circuit outputting a voltage close to a power supply voltage, a P-type MOS transistor is used as an output transistor in general. However, if the P-type MOS transistor is used as the output transistor, the following problem arises. Specifically, low drop-out is realized, but the output voltage varies with respect to variations of a load current. In order to prevent the foregoing output variations, a large-size capacitor is required as an output transistor. If the constant-voltage power circuit is applied to mobile terminals, circuits of latest mobile terminals are minimized; for this reason, it is desired to make the size of the capacitor small.