An ultralow voltage circuit for energy harvesting with 3.3 mW capacity

Abstract

This brief describes an astable multivibrator aimed to low voltage energy harvesting using inductive coupling and bipolar junction transistors. The topology needs a bias voltage at the bases, and we propose a circuit called starting block to generate this voltage from the supply. A proof-of-concept circuit with discrete devices was able to work with a voltage as low as 50 mV and deliver 3.3 mW from a 100 mV supply. To the authors’ knowledge, it is the energy harvesting circuit with highest power capacity. It has the additional advantage of using conventional devices, in contrast with other approaches that use special devices like junction field effect transistors and native metal–oxide-semiconductor field effect transistors (MOSFETs). The circuit also needs a smaller transformer when compared to its version using conventional MOSFETs.