A microminiature power converter includes a thin film magnetic induction device including a ferrite substrate and a solenoid coil conductor extending along the first and second principal planes of the substrate with the conductor extending through through-holes formed in the substrate to form a coil configuration. Electrodes are positioned near the peripheral region of the substrate and are collectively arranged at least one along the direction parallel to the axis of the solenoid coil formed by the conductor. The length of the coil can be increased to increase the inductance value of the coil. Gaps or grooves are provided near or in the peripheral region of the ferrite substrate to reduce induced voltage appearing in the electrodes.