The STTH2003CT is a 300 V, 10 A per diode fast recovery rectifier array in a common-cathode TO-220-3 package. Its 35 ns reverse recovery time (trr) cuts switching losses in continuous-current-mode PFC stages and flyback snubbers compared to a standard recovery diode.
10 A per diode — two diodes, one heatsink
Each of the two diodes in the common-cathode pair is rated for 10 A average rectified current. That means a single TO-220 can handle a 20 A centre-tapped rectifier or two independent 10 A rails, sharing one heatsink and one mounting hole. The 1.25 V forward drop at 10 A sets the conduction loss floor — about 12.5 W per diode at full current, so the thermal path to the heatsink matters.
With a 300 V DC reverse voltage rating, this diode is sized for 240 VAC input rectification (peak about 340 V) with margin, or for the boost diode in a 400 VDC bus PFC stage where the reverse voltage stays under 300 V during normal operation. It is not rated for 400 VDC bus rectification — that calls for a 600 V class part.