Voltage regulator with low drop out voltage

Abstract

A circuit and method for providing a low drop out voltage regulator. A source follower circuit is provided having a transistor (MD1) with an output terminal for driving a load at its source terminal and a voltage supply coupled to the drain terminal. At least one diode (D1) is coupled between the gate terminal and a ground reference to provide a predetermined voltage at the gate of the transistor (MD1). A voltage multiplier circuit is provided having an input (IN) for receiving an oscillating input voltage and a charge storage device (39) coupled between the oscillating input and a voltage reference (Vref), and being further coupled in series with the voltage reference and then to the gate terminal of the transistor (MD1). The oscillating input voltage is used to charge the charge storage device (39) to a voltage approximately equal to the voltage reference. When the supply voltage falls below the normal level, the series combination of the voltage reference and the charge storage device provides a multiplied voltage at the gate of the transistor, for example a voltage of twice the reference voltage. This high gate voltage keeps the output at the source of the transistor at a high voltage that is approximately equal to the supply voltage, such that the circuit provides a low drop out voltage under low supply voltage conditions.

Dependencies are inferred from the claim text.