a method and apparatus to layout planar magnetic coils on a pcb consists of maximizing the layer to layer overlap , and consequently maximizing total inductance for the given layout area , by spiraling alternating layers inward and outward . a further benefit of the matching opposite spirals is the ability to make the layer to layer electrical contacts within the magnetic field area , thus reducing leakage inductance , and minimizing the wasted extra conductor line length needed to make the connections outside the magnetic field . the reduced conductor line length results in reduced conductor line resistance . the method is applicable to voltage transformers and isolation transformers as well as simple inductors and other magnetic devices . in the transformer case the odd numbered layers are typically connected together in series to provide a larger turn ratio , and the even numbered layers are typically single turns connected together in parallel to provide more current capability .