Programmable low dropout regulators with fast transient response when programming output voltage

摘要

Apparatus and methods for programmable low dropout regulators for radio frequency (RF) electronics are provided herein. In certain configurations, a power amplifier system includes a multi-stage power amplifier that amplifies a radio frequency signal and includes a driver stage and an output stage. The power amplifier system further includes an envelope tracker that controls a supply voltage of the output stage in relation to an envelope of the radio frequency signal, and a programmable low dropout regulator that includes an output that provides a programmable supply voltage to the driver stage. The programmable low dropout regulator includes an output capacitor electrically connected to the output, a regulation transistor having a drain electrically connected to the output, and an alternative discharge circuit that discharges the output capacitor in response to programming the programmable supply voltage from a high voltage level to a low voltage level.