An Output Capacitor-Less Low Dropout Regulator Based on Push-Pull Amplifier

In this paper, a fast transient response output capacitor-less low dropout (OCL-LDO) regulator with low quiescent current is presented. A current-mode common-gate differential transconductance amplifier is paired with a push-pull output stage to achieve high slew rate at low quiescent currents. Coupling capacitors are embedded to provide feedback paths to get rid of the limit of bypass bandwidth and a pair of common-mode feedback resistors are used to adjust the dynamic current to improve the transient response performance of the error amplifier. The proposed OCL-LDO is implemented in CMOS 180 nm process, the power supply ranges from 2.5 to 4 V and achieves a stable 1.8 V output over a load range of 0.2-10 mA. The simulation results show that under the maximum load current change, the output voltage spike at 100 ps edge time is less than 340 mV, the settling time is 2.2 us, and the measured quiescent current consumption is 9.25 uA.