A 433.92-MHz CMOS Rectifier with Dynamic VTH-reduction for Wireless Biomedical Implants

A full-wave CMOS passive rectifier with an effective threshold voltage (V
TH
) reduction technique is proposed for wireless-powered biomedical implants. The V
TH
reduction is achieved by using a dynamically-biased switch and bootstrap capacitors, resulting in a significant increase in the power conversion efficiency (PCE) of the rectifier. The proposed rectifier is designed for an ISM-band frequency of 433.92 MHz and is fabricated together with two conventional bootstrap rectifiers for comparison in a 0.18-μm CMOS process. Measurement results confirm that the proposed rectifier outperforms the conventional bootstrap rectifiers in terms of the output DC voltage level and PCE. The proposed rectifier demonstrates the peak PCE of 68.5% at a load resistor of 3 kΩ at 433.92 MHz.