Patent ID: 8283906

Claim:
A voltage regulator that operates so as to keep an output voltage constant, comprising: an output transistor for outputting the output voltage; a voltage divider circuit for dividing the output voltage to be supplied to an external load to output a divided voltage; a first differential amplifier for comparing a reference voltage with the divided voltage to output a signal; a second differential amplifier for amplifying only an AC component of the output voltage, wherein the second differential amplifier has one input terminal input with the output voltage, and another input terminal input with the output voltage from which a high frequency component is removed through a low-pass filter, and amplifies only the AC component of the output voltage; and a switch for receiving an output of the second differential amplifier and short-circuiting at least one of a phase compensation resistor and the voltage divider circuit when the output voltage fluctuates by a given voltage or higher, the phase compensation resistor compensating a phase of a control terminal of the output transistor.