With the introduction of high frequency semiconductor devices and converters, wideband, lossless and accurate current measurement is the key to achieve highly efficient power conversion. Isolated wideband current measurement is required in many power electronic converters when the switching frequency is above 1 MHz. Typically current passing through a printed circuit board trace induces a highly non-uniform magnetic field which varies as a function of frequency and position relative to the trace. Magnetoresistors (MR) provide an alternative solution to isolated and contactless current monitoring in power converters. In this work, detailed characterizations of two different Magnetoresistive (MR) elements, the Anisotropic Magnetoresistor (AMR) and the Giant Magnetoresistor (GMR) are performed for contactless current sensing. The AMR and GMR sensor test circuits are designed and implemented in Printed Circuit Boards (PCB) and their performance are evaluated under different spatial and input current conditions including implementation of different sides if the board and DC, AC and step currents up to 10A. Detailed analysis is performed to analyze the sensitivity and sensing range of the sensors. Finally, a frequency analysis is performed on the step current response to evaluate the detection bandwidth of the AMR and GMR current sensors. Also, this work proposes a technique to increase the frequency bandwidth of Anisotropic Magnetoresistive (AMR) current sensors and simultaneously to intensify and normalize the field detected by the sensor in the frequency range of interest, i.e., DC-5 MHz. We demonstrate experimentally that the proposed technique yields significant enhancement in detection bandwidth of AMR current sensors.