Disclosed is a one-chip ULSI which can carry out fixed operations for a wide range of power supply voltages (1 V to 5.5 V). This one-chip ULSI is composed of a voltage converter circuit(s) which provides a fixed internal voltage for a wide range of power supply voltages, an input/output buffer which can be adapted to several input/out interface levels, a dynamic or volatile RAM(s) which can operate at a power supply voltage of 2 V or less, etc. This one-chip ULSI can be applied to compact and portable electronic devices such as a lap-top type personal computer, an electronic pocket note book, a solid-state camera, etc.