Aspects of the present disclosure include systems, structures, circuits, and methods providing integrated circuit (IC) packages or modules having a transformer with first and second spiral coils disposed on or adjacent to a substrate, each including one or more coil portions on one or multiple levels and having varying distances to an aperture or coil-origin region. A portion of a soft ferromagnetic core of the transformer can pass through the aperture or be adjacent to the coil origin region. The IC packages and modules may include various types of circuits; in some examples, IC packages or modules may include a galvanically isolated gate driver or other high voltage circuit.