A level shifter includes a level switching circuit, an input circuit, and a first voltage drop circuit. The level switching circuit is configured to adjust a first voltage level of a first node and a second voltage level of a second node in response to a first input signal and a second input signal. The input circuit is configured to receive the first input signal and the second input signal. The first voltage drop circuit is coupled between the level switching circuit and the input circuit, and is configured to track a voltage level of a third node which is coupled to the first node, in order to be turned on according to the voltage level of the third node.