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The BC548 is a general purpose NPN bipolar junction transistor found commonly in European electronic equipment and present-day designs in Australian and British electronics magazines where a commonly-available low-cost NPN transistor is required. It is a part of a family of NPN and PNP epitaxial silicon transistors that include higher-quality variants, originating in 1966 when Philips introduced the metal-cased BC108 family of transistors which became the most used transistors in Australia and taken up by many European manufacturers. The BC548 is the modern plastic packaged BC108, and can be used in any circuit designed for the BC108 or BC148, which includes many Mullard and Philips published designs. The BC546 and BC547 are essentially the same as the BC548 but selected with higher breakdown voltages while the BC549 is low noise version, and the BC550 both high-voltage and low-noise. The BC556 to BC560 are the PNP counterparts of the BC546 to BC550, respectively. The BC548 is low cost and is available in most European Union and many other countries. 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 part number is assigned by Pro Electron, which allows many manufacturers to offer electrically and physically interchangeable parts under one identification. As viewed in the image to the right, and going from left to right, lead 1 (left in diagram) is the collector, lead 2 is the base, and lead 3 is the emitter. Note that not all transistors with TO-92 cases follow this arrangement. ==Gain groupings== The type number of any of the devices in this "family" may be followed by a letter to indicate a narrow range of gain (hFE) spread (although it is not so common for a BCxx7 or BCxx8 part to be available with a "C" gain grouping). * "A" indicates low gain (110 to 220 at 2 mA), * "B" indicates medium gain (200 to 450) * "C" indicates high gain (420 to 800) So a BC548 might have a current gain anywhere between 110 and 800, but the gain of a BC548A would be within the range of 110 to 220. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「BC548」の詳細全文を読む スポンサード リンク
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