BC557 PNP General-Purpose Transistor, TO-92 (5-Piece Pack)

Most beginner transistor circuits default to NPN parts, but plenty of switching and amplification stages, particularly ones where the load needs to be switched to ground rather than to the supply rail, specifically call for a PNP transistor instead. The BC557 is the standard small-signal PNP counterpart to NPN parts like the BC547 or 2N2222, letting a circuit designer or kit-builder follow a schematic exactly as drawn rather than having to redesign the polarity around only having NPN parts on hand. Its breadboard-friendly TO-92 package and low cost make it worth keeping in any parts collection alongside its NPN counterparts, since complementary PNP/NPN pairs show up together constantly in push-pull amplifier and H-bridge-style switching designs.