Patent ID: 7710090

Claim:
A series regulator with an over current protection circuit, wherein the series regulator receives an input voltage at an input terminal and generates an output voltage and an output current at an output terminal, the series regulator comprising: a first amplifier circuit, connected between the input terminal and ground, having an inverting input that receives a reference voltage, a non-inverting input, and an output terminal; an output transistor connected between the input terminal and the output terminal, wherein a gate of the output transistor is connected to the output terminal of the first amplifier circuit; a current sense transistor having a source connected to the input terminal, and a gate connected to the output terminal of the first amplifier circuit, wherein the current sense transistor generates a sense current; a current limiting transistor connected between the input terminal and the output terminal of the first amplifier circuit, wherein the current limiting transistor controls a voltage at the gate of the output transistor; an attenuator circuit connected between the output terminal and ground, the attenuator circuit generating first and second voltage signals, wherein the first voltage signal is connected to a non-inverting input terminal of the first amplifier circuit; a voltage-to-current converter connected to the attenuator circuit and receiving the second voltage signal therefrom; a first current source connected between the voltage-to-current converter and the ground; a high ratio current mirror circuit connected to the current sense transistor, the voltage-to-current converter, and the output terminal, wherein the current mirror circuit receives the sense current from the current sense transistor and returns the sense current to the output terminal; a cascode device connected to a node between the voltage-to-current converter and the current mirror circuit; a second current source connected between the input terminal and the cascode device; and a third current source connected between the cascode device and the ground, wherein the current mirror circuit controls the gate voltage of the output transistor such that the output current generated at the output terminal is proportional to an output current of the voltage-to-current converter.