A level shifter comprises a voltage converting circuit, a voltage pull-up circuit, and a control signal generating circuit. The voltage converting circuit is configured to receive an input signal of a first voltage level and to output an output signal of a second voltage level. The voltage pull-up circuit is coupled to the voltage converting circuit and configured to expeditiously pull up a voltage of an output node of the level shifter to the second voltage level in response to a control signal. The control signal generating circuit is configured to receive the input signal and to provide the control signal to the voltage pull-up circuit. The control signal generating circuit includes three transistors.