The use of output-capacitorless class-AB CMOS low-dropout regulator for power management

Abstract

This article presents the design of a 4.5-V, 450-mA low drop-out (LDO) voltage linear regulator based on a two-stage cascoded operational transconductance amplifier (OTA) as error amplifier. The aforementioned two-stage OTA is designed with cascoded current mirroring technique to boost up the output impedance. The proposed OTA has a DC gain of 101 dB under no load condition. The designed reference voltage included in the LDO regulator is provided by a band gap reference with the temperature coefficient (T ) of 0.025 mV/ºC. The proposed LDO regulator has a maximum drop-out voltage of 0.5 V @ 450 mA of load current, and has the worst case power supply rejection ratio (PSRR) of [54.5 dB, 34.3 dB] @ [100 Hz, 10 kHz] in full load condition. All the proposed circuits are designed using a 0.35 μm CMOS technology. The design is checked in order to corroborate its performance for wide range of input voltage, founding that the circuit design works fine meeting all the initial specification requirements. Keywords-Low drop-out (LDO) voltage linear regulator; operational transconductance amplifier (OTA); band gap reference; cascoded current mirrorI.