An Output-Capacitor-less LDO with Push-pull Stage and Transient-enhanced Circuit

This article presents an output capacitor-less low dropout regulator (LDO) that achieves fast transient response through a current compensation circuit. The push-pull structure improves the voltage swing rate at the gate of the pass device and enables the gate capacitor to quickly charge and discharge when switching between light and heavy loads. The current compensation circuit is composed of logic-threshold trigged comparator (LTTC) circuit and replication transistor. When the output voltage changes, the logical threshold voltage of LTTC will change, so as to achieve the effect of comparison, to open or turn off the replication transistor, and can compensate the output current to stabilize the output voltage. The proposed structure has been implemented in CMOS 0.1S-$\mu$m standard process. The measured voltage undershoot and overshoot is 192mV and 190mV respectively with a load steps from 10$\mu$A to 500mA with 500ns edge times.