The STF826 is a PNP bipolar power transistor from STMicroelectronics, rated for 30 V collector-emitter breakdown and 3 A continuous collector current. The SOT-89-3 package keeps the footprint small while the 1.4 W maximum power dissipation handles moderate heat loads when the board copper is sized correctly.
The STF826 is listed as obsolete.
Package and mounting — SOT-89-3
The STF826 is supplied in a TO-243AA (SOT-89-3) surface-mount package. The three-lead footprint is common across many small-signal power transistors, which helps when evaluating second-source candidates.
Key ratings and the decisions they drive
The 30 V Vceo sets the maximum rail voltage — stay below that with margin for transients. The 3 A collector rating is continuous; peak currents in switching applications need to respect the 1.4 W power limit and the thermal resistance of the SOT-89-3 pad. Vce(sat) of 1.1 V at 3 A is typical for a PNP of this size; it means the on-state voltage drop will dissipate over 3 W at full current, so the duty cycle and heatsinking must be checked. The 100 MHz transition frequency is adequate for switching up to a few megahertz, but the gain roll-off at higher collector currents should be verified against the datasheet curves if operating near the 3 A limit.