Patent ID: 8384370

Claim:
A voltage regulator for outputting a constant output voltage from an output terminal, comprising: an amplifier; an output transistor; a sense transistor; a first control circuit; and a second control circuit, the amplifier making a comparison between a reference voltage and a voltage based on the output voltage, and controlling a gate voltage of the output transistor so that the output voltage becomes constant, the output transistor outputting the output voltage based on an output signal of the amplifier and a power supply voltage, the sense transistor being current-mirror-connected with the output transistor, for sensing an output current of the output transistor, the first control circuit comprising: a second transistor which is current-mirror-connected with a first transistor, the first transistor allowing a current to flow through the sense transistor, wherein the second transistor has a source connected to a ground terminal; a bias current source; a third transistor having a forward diode connection, the third transistor being provided between a power supply termnal and the bias current source; a fourth transistor which is current-mirror-connected with the third transistor; and a fifth transistor having a gate connected to a drain of the fourth transistor, and the first control circuit operating so that, when the output current becomes a maximum output current, the output transistor approaches an OFF state, based on a current flowing through the second transistor, the second control circuit comprising a sixth transistor which is current-mirror-connected with the first transistor, the second control circuit operating so that, when the output current becomes the maximum output current and the output voltage becomes equal to or lower than a predetermined voltage, the output transistor further approaches the OFF state in order that the output current becomes a short-circuit output current, based on a current flowing through the sixth transistor.