Introductory ultra-low-voltage electronics

This paper presents the fundamentals for the design of MOS analog and digital circuits that can operate at very low supply voltages. Operation of the MOS transistor in the triode region is highlighted owing to the limited voltages available. Special attention has been given to the properties of the zero-VT transistor due to its high drive capability at low voltages. Ultra-low-voltage rectifiers using diodes or diode-connected MOSFETs operating in weak inversion are analyzed. The basic amplifiers and logic gates operating at ultra-low-voltage are then reviewed. Finally, simulation and measurement results for inductive-load oscillator prototypes built in 130 nm technology demonstrate that the oscillators can operate at supply voltages of the order of the thermal voltage kT/q.