A low-drop regulator (LDO) apparatus includes an operational amplifier, a buffer stage circuit, and a power transistor. The operational amplifier is used for receiving a reference voltage and a feedback voltage to generate a first voltage. The buffer stage circuit is coupled to the power transistor and the operational amplifier and used for buffering the first voltage to generate a second voltage. The power transistor is coupled to the buffer stage circuit and used for generating an output voltage according to the second voltage wherein the output voltage is proportional to the feedback voltage. In addition, the buffer stage circuit is arranged to determine whether to mirror and generate a mirrored current according to the first voltage and to generate the second voltage for providing the second voltage to the power transistor to control on/off state of the power transistor when the mirrored current is generated.
