An ultra-low-voltage active rectifier for energy harvesting applications

This paper presents an ultra-low-voltage active rectifier for micro energy harvesting. A two stage concept is used including a first passive stage and an active diode as second stage. A bulk-input comparator design is used which is well suited for low voltage applications. The power consumption is 200 nW and the minimum operation voltage is 350 mV using a 0.35 μm low V_Th CMOS technology. The voltage drop over the rectifier is some tens of millivolt which results in voltage and power efficiencies of over 90 %. Input voltages with frequencies in the range of mHz to low kHz can be rectified.