1200 V, 2 A, 75 ns — fast recovery for high-voltage switching
It comes in a DO-201AD axial-lead through-hole package. This diode is built for high-voltage, fast-switching applications such as boost diodes in power-factor-correction stages, freewheeling diodes in flyback converters, and snubber clamping in motor drives.
A 75 ns reverse recovery time places this diode in the fast-recovery class, suitable for switching frequencies in the tens of kilohertz. In a continuous-conduction-mode PFC boost stage, the 75 ns trr limits the reverse-recovery charge that the MOSFET must absorb, reducing turn-on loss and ringing. The 1.75 V forward drop at 2 A is a trade-off for the speed — expect higher conduction loss than a slower 1200 V standard-recovery diode, but lower switching loss overall.
STMicroelectronics lists the STTH212RL as Obsolete. The base product number STTH21 family may include active variants, but this specific RL suffix (Tape & Reel, DO-201AD) is no longer in production.
Through-hole axial — retrofit and handling
The DO-201AD axial package is a standard through-hole form factor. When replacing this diode in a legacy board, confirm the lead spacing and body diameter match the existing footprint.