A low-area power-efficient CMOS active rectifier for wirelessly powered medical devices

We present in this paper a new full-wave active rectifier topology. It uses a single bootstrapped capacitor to reduce the effective threshold voltage of selected MOS switches in both positive and negative input source cycles. It achieves a significant saving in silicon area while having a remarkably high power efficiency and low voltage drop. The structure does not require complex circuit design. A simple direct control scheme is used to connect the bootstrapped reservoir to the main pass switches at proper time. The highest voltages available in the circuit are used to drive the gates of selected transistors in order to reduce the leakages and to lower their channel on-resistance, while having high transconductance. The new design benefits from low-threshold MOS available in advanced CMOS technologies. The proposed rectifier was implemented using the standard TSMC 0.18 µm CMOS process and then characterized with the SpectreS simulator. The circuit was laid out and reported post-layout simulation results were found in good agreement with schematics-based simulations. The design saves almost 70% area compared to a previously reported double capacitor structure.