This study proposes a 300-mA external capacitor-free low-dropout (LDO) regulator for system-on-chip and embedded applications. To achieve a full-load range from 0 to 300 mA, a two-scheme (a light-load case and a heavy-load case) operation LDO regulator with a novel control circuit is proposed. In the light-load case (0-0.5 mA), only one P-type metal-oxide-semiconductor input-pair amplifier with a 10-pF on-chip capacitor is used to obtain a load current as low as 0. In the heavy-load case (0.5 to 300 mA), both Ptype metal-oxide-semiconductor and N-type metal-oxide-semiconductor differential input-pair amplifiers with an assistant push-pull stage are utilized to improve the stability of the LDO regulator and achieve a high slew rate and fast-transient response. Measurements show an output voltage of 3.3 V and a full output load range from 0 to 300 mA. A line regulation of 1.66 mV/V and a load regulation of 0.0334 mV/mA are achieved. The measured power-supply rejection ratio at 1 kHz is À65 dB, and the measured output noise is only 34 μV. The total active chip size is approximately 0.4 mm 2 with a standard 0.5 μm complementary metal-oxide-semiconductor process.

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