Effect of Varying Threshold Voltage on Efficiency of CMOS Rectifiers for Piezoelectric Energy Harvesting Applications

In this paper, the efficiency of a conventional cross-coupled gate CMOS bridge rectifier used in MEMS (microelectromechanical system) piezoelectric energy harvesters is investigated. The MOSFET threshold voltage is varied between 10 mV and 800 mV to evaluate the performance of the circuit for various threshold voltage levels. The circuit is simulated using the 130 nm CMOS technology process for each MOSFET to generate performance metrics for the rectifier. The results are evaluated for optimal load resistance, and it is confirmed that a lower threshold voltage results in significant improvements to the efficiency of the rectifier at lower input voltage amplitudes, with up to 62% at 0.5 V input amplitude when a smoothing capacitor is placed across the load.