An ultra-low power CMOS subthreshold voltage reference without requiring resistors or BJTs

This paper presents a novel ultra-low power voltage reference operational from supply voltage down to less than 0.9V. In the proposed reference circuit, the PTAT voltage is generated by feeding the leakage current of a zero-Vgs NMOS transistor to two diode-connected NMOS transistors, both of which are in subthreshold region; while the CTAT voltage is created by using the body-diodes of another NMOS transistor. Consequently, low-voltage, low-power operation can be achieved without requiring resistors or BJTs, hence with small chip area consumption. The proposed circuit is designed in a 0.18-μm process. Simulation results show that it is capable of providing an 808mV reference voltage with 10ppm/°C from −30°C–125°C even with only 900mV supply voltage. Moreover, the typical power consumption is only 10nW.