Patent ID: 7863874

Claim:
A linear voltage regulator for regulating an output voltage, comprising: a first transistor, which is connected between a terminal for an input voltage and a terminal for the output voltage; a reference voltage source for producing a first reference voltage; a first resistor; a second resistor; a second transistor, wherein the first resistor, the second transistor, and the second resistor are series-connected between the terminal for the output voltage and a second reference voltage and constitute a voltage divider, and wherein a divided output voltage is present at a tap of the voltage divider; and a differential amplifier having an inverting input and a non-inverting input, wherein the inverting input is connected to the reference voltage source, the non-inverting input is connected to the tap of the voltage divider, and an output terminal of the differential amplifier is connected to a control terminal of the first transistor, and wherein, in a normal operating mode the output voltage is independent of the value of the input voltage and the second transistor is turned substantially fully on, and wherein, not in the normal operating mode, a drain-source resistance of the second transistor increases sharply with decreasing input voltage causing the divided output voltage at a tap of the voltage divider to decrease disproportionately to the output voltage.