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BC548

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BC548

The BC548 is a general-purpose NPN bipolar junction transistor commonly used in European electronic equipment. It is notably 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.

Contents

History and usage

The BC548 is a part of a higher-quality family of NPN and PNP epitaxial silicon transistors that originated with the metal-cased BC108 family of transistors. This series, introduced in 1966 by Philips, became the most used transistors in Australia and was 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.

As of 2016, the BC548 is principally produced by ON Semiconductor and Fairchild Semiconductor.

Pinout and specifications

As viewed in the top-right image, going from left to right, the pinout is as follows: lead 1 (left in diagram) is the collector, lead 2 is the base, and lead 3 is the emitter.

The BC548 part number is assigned by Pro Electron, which allows many manufacturers to offer electrically and physically interchangeable parts under one identification. Devices registered to this Pro Electron number must have the following minimum performance characteristics:

  • Breakdown voltage, collector-to-emitter with base open-circuit VCEO = 30 V (see below)
  • Rated continuous collector current IC = 100 mA (Fairchild's BC548 at one time had a higher rating)
  • Rated total power dissipation Ptotal = 500 mW (some manufacturers may specify 625 mW - see below)
  • Transition frequency (gain-bandwidth product) ft = 150 MHz minimum (300 MHz typical)

    • Variants

    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.

    Some manufacturers specify their parts with higher ratings, for example the Fairchild 1997 datasheet (547ABC, Rev B) for the BC547, sourced from Process 10 gave 500mA as the maximum collector current, while their datasheets dated 2002 have dropped the current rating to the standard 100mA.

    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.

    The PNP counterparts of the BC546 to BC550 are the BC556 to BC560 respectively, i.e. the type numbers are higher by ten.

    The surface-mount package versions are the BC846 to BC850 (and PNP versions: BC856 to BC860).

    References

    BC548 Wikipedia
    (Text) CC BY-SA