The STMicroelectronics STD1805T4 is an NPN bipolar power transistor in a DPAK (TO-252-3) surface-mount package, rated for 60 V collector-emitter breakdown and 5 A continuous collector current. It handles up to 15 W of power dissipation and transitions at 150 MHz, making it a general-purpose switching and linear amplifier device for medium-power DC-DC converters, linear regulators, relay drivers, and motor control circuits in industrial and automotive auxiliary loads.
The 60 V Vce breakdown and 5 A Ic rating define the safe operating area for a substitute. The 600 mV Vce saturation at 200 mA base current and 5 A collector current is typical for a 5 A NPN in DPAK — a replacement with lower Vce(sat) improves efficiency in switching applications. The DC current gain of 200 minimum at 100 mA, 2 V is generous, so a substitute with hFE in the 100–300 range at similar bias will work without redesigning the base drive. The 100 nA collector cutoff ensures low leakage in off-state, important for battery-powered or high-impedance loads.
Package and footprint note
The DPAK (TO-252-3) footprint is standard — two leads plus a tab that is the collector. Any pin-compatible NPN in the same package will drop in without board changes.