240 V small-signal switch in a SOT-89 footprint
The Infineon BSS87H6327FTSA1 is an N-channel enhancement-mode MOSFET from the SIPMOS® family, rated for 240 V drain-to-source and 260 mA continuous drain current. The SOT-89 (PG-SOT89-4-2) package keeps the board footprint compact — the centre tab is the drain, and the copper area under it sets the thermal resistance to ambient for the 1 W power dissipation limit.
The 240 V Vdss gives headroom for 48 V, 72 V, and 120 V DC rails in industrial control, auxiliary power supplies, and telecom line cards — the 150°C junction rating means it can sit near a hot transformer or heatsink without derating the voltage. The 6 Ohm Rds(on) at 10 V gate drive is moderate for a 240 V device; at 260 mA the conduction loss is about 0.4 W, which fits within the 1 W package limit when the board has reasonable copper area. The 1.8 V typical gate threshold at 108 µA means the device can be driven from a 3.3 V logic output with a series gate resistor — the 4.5 V minimum drive voltage for the rated Rds(on) is the practical floor for full enhancement.
Temperature range and environment
The 150°C upper limit allows the device to operate near a 125°C ambient with the 1 W dissipation budget, provided the board layout pulls heat away from the SOT-89 tab.