A Sub-500 mV Highly Efficient Active Rectifier for Energy Harvesting Applications

This paper presents a highly efficient, ultra-low-voltage active full wave rectifier. A two-stage concept is used including a first passive stage and only one active diode as second stage. A bulk-input comparator working in the subthreshold region is used to drive the switch of the active diode. The voltage drop over the rectifier is some tens of millivolt, which results in voltage and power efficiencies of over 90%. The design was successfully implemented in an 0.35 mu m CMOS technology. The measured power consumption of the comparator is 266 nW@500 mV and the minimum operating voltage is 380 mV. Input voltages with frequencies up to 10 kHz can be rectified.