TM71 is a high-permeability MnZn power ferrite with an initial permeability (μi) of 3800, the highest in the power series, a saturation flux density (Bs) of 550 mT at 25 °C (425 mT at 100 °C) and a Curie temperature above 255 °C. Its coercivity (Hc) is 6 A/m at 25 °C (2.5 A/m at 100 °C) and its relative loss factor at 100 kHz is below 4×10⁻⁶: high μi and low Hc minimise the number of turns and the magnetising current for a given inductance, giving fast pulse droop and recovery. Its loss is, however, temperature-sensitive: Pcv at 100 kHz / 200 mT rises from 400 kW/m³ at 25 °C to 1100 kW/m³ at 100 °C and at 500 kHz / 50 mT from 190 to 525 kW/m³, so it is not a low-loss grade at elevated temperature. Typical applications are gate-drive and pulse transformers, signal isolation transformers, and low-flux storage and filter inductors. Of the two high-Bs special grades TM71 is distinguished by μi rather than loss (TM82 by its 600 mT Bs and DC-bias tolerance): main transformers operating hot or at large flux swing should use the mid-frequency grades TM80/TM83. Its DC-bias capability leads at 25 °C but no longer at 100 °C owing to the rise in loss, so selection should be based on the actual core temperature.