Patent ID: 8436603

Claim:
A voltage regulator, comprising: a reference voltage circuit connected between a power supply input terminal and a ground terminal, for generating a reference voltage which is constant, independently of a power supply input; an output transistor connected between the power supply input terminal and an output voltage terminal, for generating an output voltage which is constant, independently of an output current; a voltage dividing circuit connected between the output voltage terminal and the ground terminal, for dividing the output voltage to generate a referred voltage; a first differential amplifier circuit for generating a first differential amplifier output voltage based on the reference voltage received as a non-inverting input and the referred voltage received as an inverting input; a second differential amplifier circuit for controlling a control terminal of the output transistor based on the output voltage, the referred voltage received as a non-inverting input, the reference voltage received as a first inverting input, and the first differential amplifier output voltage received as a second inverting input; at least one bias circuit for supplying a bias current to the first differential amplifier circuit and the second differential amplifier circuit; and a control circuit for controlling the first differential amplifier circuit and the second differential amplifier circuit based on an operation control signal having at least a binary value such that the voltage regulator is operable to switch between a two-stage structure operation for low current consumption and a three-stage structure operation for high transient response characteristic, wherein when the operation control signal has a first logic value, the first differential amplifier circuit is in a suspended state, thereby switching the voltage regulator to the two-stage structure operation with the second differential amplifier and the output transistor; and wherein when the operation control signal has a second logic value, the first differential amplifier circuit is in an operating state, thereby switching the voltage regulator to the three-stage structure operation with the first differential amplifier, the second differential amplifier and the output transistor.