A 0.12–0.4 V, Versatile 3-Transistor CMOS Voltage Reference for Ultra-Low Power Systems

In this paper, we propose an ultra-low power compact 3-transistor voltage reference capable of operating at ultra-low supply voltages. The proposed circuit is based on the self-cascode MOSFET (SCM), which provides a reference voltage proportional to the threshold voltage (VT) difference of the two NMOS transistors that compose it. Reverse short-channel and narrow-width effects are explored to obtain such VT difference while using the same type of transistor. Ultra-low power operation and low line sensitivity is achieved by biasing the SCM with a zero-VT (native) transistor, also leading to an area efficient design. To show its versatility, three versions of the proposed circuit were fabricated in a standard 0.13-μm CMOS process. Measurement performed over five samples showed an average temperature coefficient of 150-1500 ppm/°C. Minimum supply voltages of 0.12-0.4 V was observed while providing reference voltages around tens of mV. The proposed circuits consume 0.33-50 pW at room temperature and minimum supply voltage. The occupied area for any version is less than 0.0012 mm2.