Network transformer structures including a production method therefore are disclosed. In one embodiment, multiple integrated I-shaped magnetic cores that include three winding barrel portions based on a new design for a magnetic core structure is disclosed. A first winding barrel portion and a second winding barrel portion are configured to wind a transformer winding, and a third winding barrel portion is configured to wind a common mode choke winding, so that a transformer and a common mode choke are combined onto one magnetic core to replace two previous magnetic cores, thereby saving on the overall network transformer structure cost as well as space on, for example, an end consumer printed circuit board.