Digital/analog core power supplies such as CMOS image sensors, MCUs, and RFs, may cause malfunction or performance degradation due to external noises. Therefore, we need to be able to remove switching noise from DC-DC converters etc. of external power supplies, which are sources of noise. In other words, we need to have a higher ripple rejection ratio. In addition to the low-frequency range from DC to 1 kHz, our LDO regulator has a high ripple removal capability up to a high-frequency range from 100 kHz to several MHz, and can be used as a high-quality power supply with low noise.