BD139, BD140 are epitaxial planar transistors which are mounted in the SOT-32 plastic package. They are designed for audio amplifiers and drivers utilizing complementary or quasi-complementary circuits. The NPN types are the BD135 and BD139, and the complementary PNP types are the BD136 and BD140.
They are used in Medium Power Linear and Switching Applications. BD135, BD137 and BD139 are complement to BD136, BD138 and BD140 respectively.