US Patent 7176740 Level conversion circuit

A level conversion circuit that prevents the operation speed from decreasing when the power supply voltage decreases while appropriately performing level conversion. The level conversion circuit includes first and second PMOS transistors. A first NMOS transistor is connected to the first PMOS transistor and the second PMOS transistor. A second NMOS transistor is connected to the second PMOS transistor and the first PMOS transistor. A bias circuit, connected to the first and second NMOS transistors, generates a bias potential that is supplied to the first and second NMOS transistors and that is greater than the first voltage by a threshold voltage of the first and second NMOS transistors. The bias circuit further controls current, which determines the bias potential and flows to the bias circuit, in accordance with a control signal having the first voltage.