A method and circuits to improve the stability of low dropout voltage regulators
having an adaptive biased driving stage. Said improvement of stabilization is valid
through the total range of output current possible. A serial impedance is added
to the gate capacitance of the PMOS pass device of said LDO. Said serial impedance
could be a resistor or a transistor. In case of low load currents said impedance
is not dominating, for high load currents said impedance keeps the gate pole close
to the resonance frequency of the output tank. In case of medium load currents,
wherein the inner resistance of the driving stage is about equal to said serial
impedance, the gate pole could get too low. This problem is solved by reducing
said serial impedance by shunting. Said shunting can be performed stepwise depending
on the size of the load current. A special circuitry detects the condition of medium
load currents and can initialize the shunting of said serial impedance accordingly
in order to keep the gate pole on the optimum frequency.