Based on electric and magnetic properties, like high saturation magnetization, high initial permeability, low core loss, high resistivity, low coercivity, zero or low magnetostriction, amorphous and nanocrystalline alloys have been used in some electromagnetic devices applications such as: common mode choke coils, pulse transformers, current transformers, impulse current transformers, transformers for switched-mode power supplies. In many industrial applications designers need magnetic core material with the ability to have good soft magnetic properties. Each of core type must be developed for a specific application, therefore they all have advantages and drawback; for instance, the proliferation of high-efficiency electrical power loads, and their concomitant sensitivity to disturbances, has imposed stringent requirements on the power supply quality. The following is an overview of the electromagnetic core design of some these devices.