Darlington npn transistors st bd679 darlington power transistor npn polarity 80v collector emitter voltage vceo 80v collector base voltage vcbo 5v emitter base voltage veb 4a collector current 40w power 750 dc current gain hfe 05ma collector cut off current 25v collector emitter saturation voltage sot 32 case tube complementary good hfe linearity high transition frequency monolithic darlington configuration with integrated anti parallel collector emitter diode typica