A level shifter includes a first level shift module for producing a shifted signal by adjusting a direct current (DC) level of an input signal by a first bias voltage having a first polarity. A second level shift module produces an output signal by adjusting a DC level of the shifted signal by a second bias voltage having a second polarity. The first polarity is opposite to the second polarity and the sum of the first bias voltage and the second bias voltage is a non-zero voltage.