An Active Rectifier/Regulator Combo Circuit for Powering Biomedical Implants

A circuit that combines an active rectifier and a linear regulator, which will be referred to as a rectulator, is proposed in this paper. The main transistor in the rectulator is used for both the rectification of the AC input (V-AC) and the regulation of the DC output (V-O) to reduce the overall voltage drop between V-AC and V-O. The rectulator has a high power efficiency (h(P)) and very good amplitude modulation (AM) rejection on V-AC against AC field strength variations. A full-wave rectulator implemented in a 0.18 mm CMOS process showed an AM rejection > 45dB for an AM frequency < 2kHz. A h(P) of 90.7% was measured for an input frequency of 5MHz, V-O = 2.5V and an output power of 10.5mW.