BD140 PNP Bipolar Medium-Power Transistor (TO-126)

The BD140 is the PNP half of the BD139/BD140 complementary pair, a combination that appears together constantly in classic transistor-based audio amplifier output stages, where one of each polarity handles alternating halves of the signal waveform. Beyond that specific role, it serves the same general medium-power switching and amplification purposes as the BD139 whenever a circuit needs a PNP part in that same current-handling range. Stocking both halves of the pair together is practical since so many published designs that use one explicitly need the other as its complementary match.