L43 is a NiZn ferrite with an initial permeability (μi) of approx. 800, a saturation flux density (Bs) of approx. 350 mT at 25 °C (245 mT at 100 °C) and a Curie temperature above 160 °C. It is the mainstay EMI-suppression grade: the loss factor is only 20×10⁻⁶ at 0.1 MHz under low flux, while above a few tens of MHz the μ″ loss component rises rapidly and the impedance becomes resistance-dominated, dissipating common-mode noise as heat instead of reflecting it back into the line. Its normalized-impedance curves are given for two fixtures — a T31×19×8 toroid and an RH5×1.5×10 bead (see next page): consult the toroid data for common-mode chokes and larger rings, the bead data for beads and sleeves. Typical uses are EMI suppression filters, common-mode chokes, signal-line suppression rings and power-inlet filtering, as well as RFID antennas. Among the three grades at a nominal μi of approx. 800, L43 leads in broadband suppression (choose SL80 for temperature stability, G5A for high-Bs differential-mode/power); within the L family L43 has the widest band — for higher impedance at lower frequencies step up to L6A (μi approx. 1200), L8A (approx. 1600) or L22A/L28A (2200/2800).