A circuit includes a bias circuit and a level shifter. The bias circuit includes first and second input terminals configured to receive first and second power supply voltages, and is configured to generate a bias voltage having the greater of a first voltage level of the first power supply voltage or a second voltage level of the second power supply voltage. The level shifter includes a first PMOS transistor configured to receive the first power supply voltage and a second PMOS transistor configured to receive the second power supply voltage, and each of the first and second PMOS transistors includes a bulk terminal configured to receive the bias voltage.