Patent ID: 8294442

Claim:
A low dropout regulator circuit without external capacitors rapidly responding to load change, comprising: a slow path for controlling voltage comprising an operational amplifier I 0 ; a fast path for controlling voltage comprising a comparator I 1 , a comparator I 2 , a field effect transistor MN 1 and a field effect transistor MN 2 ; a shared branch comprising a driving transistor MPR, a resistor RF 1 and a resistor RF 2 , wherein said operational amplifier I 0 , driving transistor MPR, resistor RF 1 and resistor RF 2 form an operational amplifier loop for providing an accurate output voltage, said comparator I 1 , comparator I 2 , field effect transistor MN 1 , field effect transistor MN 2 , driving transistor MPR, resistor RF 1 and resistor RF 2 form a comparator loop for responding to rapid load change; and a reference voltage generating circuit I 3 for providing said operational amplifier I 0 , said comparator I 1 and said comparator I 2 with three reference voltages VR, VRL and VRH respectively, wherein a relationship among said three reference voltages is VRH>VR>VRL.