45 ns reverse recovery — the switching window
The STTH8R06D is a 600 V, 8 A fast recovery diode from STMicroelectronics in a TO-220AC through-hole package. Its 45 ns reverse recovery time (trr) places it in the standard ultrafast class. The 45 ns trr is specified at typical test conditions; actual recovery charge and softness factor vary with forward current and dI/dt.
Thermal headroom at 175°C junction
Rated for a maximum junction temperature of 175°C, the STTH8R06D offers a 25°C margin over 150°C-rated diodes. In a forced-air PFC stage with a 4 A average current and a modest heatsink, that extra headroom keeps the junction below the derating threshold even when the ambient inside the enclosure reaches 85°C. The 2.9 V forward voltage at 8 A (25°C) sets the conduction loss floor at 23.2 W peak. The TO-220AC tab must be heatsinked with a thermal resistance low enough to keep Tj below 175°C at the average current — a 10°C/W heatsink in 50°C ambient gives about 12.5 W dissipation budget before hitting the limit.
The 30 µA reverse leakage at 600 V (25°C) is typical for a fast epitaxial diode at this voltage class; leakage doubles roughly every 10°C rise, so at 125°C junction expect leakage in the low milliamps — budget for it in standby loss calculations.