Design of LDO linear regulator with ultra low-output impedance buffer

This paper presents a low-dropout (LDO) linear regulator using ultra-low output resistance buffer for frequency compensation. The proposed buffer achieves ultra low output impedance with dual shunt feedback loops, which makes it possible to improve load and line regulations as well as the transient response for low voltage applications. A reference control scheme for programmable output voltage of the LDO is presented. The designed LDO linear regulator works under the input voltage of 2.5~5.5 V and provides up to 300 mA load current for an output voltage range of 0.6~3.3 V.