PNP power switch for 12–24 V rails
The STMicroelectronics STD826T4 is a PNP bipolar power transistor in the DPAK (TO-252-3) surface-mount package, rated for 30 V collector-emitter breakdown and 3 A continuous collector current. Its 100 MHz transition frequency makes it suitable for moderate-speed switching applications such as load switches, relay drivers, and solenoid drivers in 12 V or 24 V systems. The 15 W power dissipation ceiling, combined with the DPAK's exposed tab, requires attention to PCB copper area and thermal vias for continuous operation near the rating.
Vce(sat) and hFE — what they mean for drive margin
The 1.1 V maximum Vce(sat) at 150 mA base drive and 3 A collector current means the transistor drops about 1.1 V when fully saturated. For a 12 V rail, that leaves roughly 10.9 V across the load — acceptable for relays and solenoids that tolerate a few volts of drop. The minimum DC current gain of 100 at 100 mA collector current and 2 V Vce gives good base-drive efficiency; a 30 mA base current can saturate a 3 A load. At lower collector currents the gain is typically higher, so the drive stage can be designed around the 100 minimum without over-specifying the base resistor.
No direct factory replacement is listed on the lifecycle record. For new designs, a current-production PNP transistor in the same voltage and current class (e.g., 30–40 V, 3–5 A, DPAK) should be evaluated — parametric fit will depend on the specific drive and switching requirements.