Light load stability circuitry for LDO regulator

A method performed by a linear regulator circuit for generating a regulated output voltage comprising:

• applying a reference voltage to a first input of an error amplifier:
• applying a signal, corresponding to an output voltage of the regulator, to a second input of the error amplifier;
• driving a base of a bipolar pass transistor, the pass transistor being connected between an input voltage and a load, by a driver controlled by an output of the error amplifier to cause the voltage at the second input to substantially equal the reference voltage at the first input;
• providing negative feedback of an AC signal generated by the error amplifier by an AC-coupled feedback circuit, the feedback circuit comprising:
• a bipolar feedback transistor having a base coupled to the base of the pass transistor;
• an emitter resistor coupled to the emitter of the feedback transistor;
• and
• a feedback capacitor coupled between a collector of the feedback transistor and the output of the error amplifier,
• the feedback circuit performing the method comprising:
• lowering an output impedance at the output of the error amplifier for AC signals at load currents below a certain threshold to increase a phase margin of the regulator, wherein the feedback circuit is substantially ineffectual at load currents substantially above the threshold.