This brief presents an ultra-low power low-dropout (LDO) regulator with an experimental total quiescent current consumption of only 3.08 nA. The circuit is designed to operate with a load current in the range 0 - 11 mA. A novel adaptive biasing scheme based on a super source follower (SSF) structure is proposed, which measures the absolute voltage difference between the two inputs of the LDO’s error amplifier and modifies the biasing current accordingly. Thus, the transient response of the regulator is improved by counteracting the effect of using such a low bias current. The proposed LDO has been fabricated in a standard CMOS 180 nm process and the experimental characterization showed an outstanding performance in terms of maximum load current over quiescent current consumption ratio.
Keywords: adaptive biasing, analog integrated circuit, capacitor-less LDO, low-power