The BD139 is a NPN complementary low voltage NPN transistor in 3 pin Its package is TO-126. This device is designed for audio amplifiers and drivers utilizing complementary or quasi-complementary circuits. Type Medium Power NPN transistor Maximum collector power dissipation (Pc) 12 W Maximum collector-base voltage Vcb 80 V Maximum emitter-base voltage 5 V Maximum collector current 1.5 A Applications Medium Power and Liner Switching