This paper presents a novel integrated wireless power transfer receiver for implantable medical devices, including a load-modulation feedback loop and an active rectifier with maximum efficiency tracking technique. The feedback loop enables the control of the power delivered to the load by means of a frequency modulation of the receiver load; the active rectifier maximizes the efficiency of the link through a second feedback calibration loop of the off-transition of the active diodes, showing high VRC and PCE for a wide range of load conditions.