A sub-1V 115nA 0.35µm CMOS voltage reference for ultra low-power applications

A voltage reference circuit capable of sub-1 V operation and with ultra-low power consumption is introduced in this paper. In the proposed circuit, proportional-to-absolute-temperature voltage is generated by using the series-connection of two NMOS devices working in sub-threshold region and the gate-to-source voltage of another NMOS device is adopted to realize the complementary-to-absolute-temperature voltage. Moreover, the temperature compensation is performed by using a switch-capacitor circuit. The proposed circuit is implemented in chartered 0.35 μm CMOS technology and occupies an active chip area of 0.021 mm
²
. Post-layout simulation results show that it can operate with a supply voltage down to 0.9 V while consuming 115 nA ground current. With 1 V power supply, the output voltage is 142.8 mV at 25°C and the temperature coefficient is 25.5 ppm/°C.