BDX53B Copy MPN

The BDX53B is an NPN Darlington transistor in a TO-220 through-hole package, rated for 80 V collector-emitter breakdown and 8 A continuous collector current. The Darlington pair gives a minimum DC current gain of 750 at 3 A collector current and 3 V VCE, so the base drive requirement stays low — about 12 mA base current to saturate the output at 3 A. That gain margin means a simple microcontroller GPIO through a resistor can drive it, no separate driver stage needed. Maximum power dissipation is 60 W, which sets the thermal budget. In a TO-220 package that figure assumes the device is bolted to an infinite heatsink — real-world derating depends on the thermal interface and ambient.