An ignition apparatus includes a cylindrical core made from magnetically-permeable material and a C-shaped magnetic return path structure that is made from a stack of silicon steel laminations. A tightly controlled air gap is provided between one leg of the C-shaped structure and an end face of the core, forming a magnetic circuit having a high magnetic permeability, which overall reduces the number of primary winding turns needed, thereby reducing the amount of copper wire. In addition, the circular cross-section of the core reduces the mean length per turn (MLT) of the primary winding because the primary winding can be wound directly on the core, which in turn also reduces the MLT of the secondary winding. The reduced MLT also reduces the amount of copper wire. The structure may be replaced using a magnetically-permeable, U-shaped shield.