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

Abstract

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 ( $V_{T}$ ) difference of the two NMOS transistors that compose it. Reverse short-channel and narrow-width effects are explored to obtain such $V_{T}$ 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- $V_{T}$ (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- $\mu \text{m}$ 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.