US Patent 7741872 Level shifter

A level shifter for shifting an input signal to an output signal. The level shifter includes an input buffer biased a first voltage and a ground voltage; an output buffer and a level-processing unit both biased between a second voltage and the ground voltage; and a voltage-drop unit coupled to the level-processing unit and biased between the first voltage and the second voltage. While the first voltage is in an OFF state and the second voltage is switched on, the voltage-drop unit provides an initializing voltage for the level-processing unit according to the second voltage to shift the input signal to provide the output signal.