A contactless power receiver is provided with a dynamically tuned pick up coil. The power transfer capacity of this power receiver is dynamically tuned using semiconductor devices that are operated in linear mode over part of their operation. The semiconductor devices are driven by a controller that is configured to implement a range of control strategies depending on system requirements. The semiconductor device may be used by itself or in conjunction with reactive elements to dynamically tune the pick up coil. In some implementations the contactless power receiver maybe configured to work with a consumer electronic or a wireless sensor device. The contactless power receiver can be integrated with the energy storage component of the device to provide a retrofit solution for existing products. The device can then be placed in vicinity of a planar magnetic field generated by a charging pad.