BC548
general-purpose NPN bipolar junction transistor
The BC548 is a general-purpose NPN bipolar junction transistor commonly used in European and American electronic equipment. Notably, it is often the first type of bipolar transistor hobbyists encounter and is often featured in designs in hobby electronics magazines where a general-purpose transistor is required. The BC548 is low in cost and widely available.
History and usage
The BC548 is a part of a family of NPN and PNP planar epitaxial silicon transistors that originated with the metal-cased BC108 family of transistors. The BC548 is the modern plastic-packaged BC108; the BC548 article at the Radiomuseum website describes the BC548 as a successor to the BC238 and differing from the BC108 in only the shape of the package. Datasheets for the BC548 give specifications that are identical to, or exceed, those of the BC108, BC148 and BC238 predecessors. Thus the BC548 (or BC546 to 550) is a valid substitute in any circuit designed for the older BC108 (or BC148), which includes many Mullard and Philips published designs.
Pinout and specifications
The BC548 is supplied in a standard TO-92 3-pin package. The assignment of transistor elements (b, c, e) to leads, i.e. the "pinout", follows the same convention used by some – but not all – other TO-92 devices.
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