800 V, 1 A, 75 ns — a fast-recovery axial diode for PFC and snubber duty
The STTH108RL is a 1 A, 800 V fast-recovery rectifier from STMicroelectronics in a DO-41 axial-lead package. Its 75 ns reverse recovery time (trr) makes it suitable for continuous-conduction-mode PFC boost stages, output rectification in flyback converters, and snubber clamping where recovery loss matters. The 800 V reverse voltage rating provides derating margin on a 400 V DC bus or 480 VAC rectified line.
A 75 ns trr at 1 A forward current and 800 V blocking means this diode can switch in the 50–100 kHz range without excessive turn-off loss. In a CCM PFC stage, that recovery charge directly affects the MOSFET's turn-on loss and the EMI signature. The 1.65 V forward drop at 1 A is typical for a fast-recovery part in this voltage class — expect a few degrees of junction rise in free-air, but the 175 °C max junction rating gives headroom if you heatsink the leads or mount in forced airflow.
STMicroelectronics lists the STTH108RL as obsolete. The last-time-buy window has closed, so new production is not available from the factory. Independent distribution and surplus channels remain the supply path. For a new design, consider the active STTH1R06 or STTH1L06 family members in the same DO-41 footprint — they share the 1 A rating and axial package, with 30 ns or 50 ns trr options at 600 V.