Patent ID: 7893566

Claim:
A circuit that connects the higher voltage of two power supplies to an output, the circuit comprising: a first transistor with its source connected to a first power supply and its gate to a second power supply; a second transistor with its source connected to the second power supply and its gate to the first power supply; cross coupled first and second inverters, the first inverter input connected to the first transistor drain and the second inverter input connected to the second transistor drain; the first inverter powered by the second power supply and the second inverter powered by the first power supply; the input of the first inverter connected to the output of the second inverter, and the input of the second inverter connected to the output of the first inverter; a third transistor with its gate connected to the drain of the second transistor, its source connected to the first power supply and its drain connected to the output voltage; and a fourth transistor with its gate connected to the first transistor drain, its source connected to the second power supply and its drain connected to the output.