As stated previously a differential mode choke is really just a single winding inductor. As shown in the top left diagram the line current, shown in red, flows through the inductor winding, shown in yellow, and this creates a magnetic field within the core, shown in blue. The differential mode inductor must provide the required inductance/impedance with a low enough winding resistance to ensure the part does not have excessive losses or overheat. In addition the part must be able to withstand the peak current without saturating. The top right drawing shows the simplified reluctance model of a differential mode choke. The source in the magnetic model is the line current (Iline) times the number of turns (N) which creates the flux, shown in blue, which flows through the reluctance. From the above equations it can be seen that the peak flux density is equal to the inductance times the peak line current divided by the turns, times the cross sectional area of the core. Because of the need to handle the DC offset, DM chokes often use either powdered iron or gapped ferrite cores. As a design example a 350µH, 2A differential mode choke was created using a 0.8” OD, 75 perm powdered iron core with 54 turns of 23 GA wire. This design would yield a resistance of 180mΩ (720mW of loss) and be approximately 4.76cm³.