Low propagation delay level shifter

A level shifter includes a low-level adjustment circuit, a comparator circuit, and a high-level adjustment circuit. The low-level adjustment circuit pulls down a level of one of a first input node and a second input node to a first low supply voltage. The comparator outputs a one having higher level in the level of the first input level and a second low supply voltage to a first output node, in which the second low supply voltage is higher than the first low supply voltage. The high-level adjustment circuit selectively adjusts the level of the first output node according to the level of the first input node and the level of the second input node to generate the output signal.