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[[Image:TO-92, BC548 (front, shaded).svg|thumb|BC548 transistor]] |
[[Image:TO-92, BC548 (front, shaded).svg|thumb|BC548 transistor]] |
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The '''BC548''' is a general purpose [[silicon transistor|silicon]] [[NPN transistor|NPN]] [[bipolar junction transistor|BJT]] [[transistor]] found commonly in European electronic equipment. |
The '''BC548''' is a general purpose [[silicon transistor|silicon]] [[NPN transistor|NPN]] [[bipolar junction transistor|BJT]] [[transistor]] found commonly in European electronic equipment. |
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⚫ | If the [[TO-92]] package is held in front of one's face with the flat side facing toward you and the leads downward, (see picture) the order of the leads, from left to right is ''collector, base, emitter''. |
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==Specifications== |
==Specifications== |
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:V<sub>cbo</sub> = 30 [[volt|V]] |
:V<sub>cbo</sub> = 30 [[volt|V]] |
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:I<sub>c</sub> = 100 [[milliampere|mA]] |
:I<sub>c</sub> = 100 [[milliampere|mA]] |
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:P<sub>total</sub> = 50 [[milliwatt|mW]] |
:P<sub>total</sub> = 50 [[milliwatt|mW]] |
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:f<sub>t</sub> = 300 [[megahertz|MHz]] |
:f<sub>t</sub> = 300 [[megahertz|MHz]] |
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:<ref>World's Transistor Comparison Tables, Tech/ECA, 1993, ISBN 981-214-444-7</ref> |
:<ref>World's Transistor Comparison Tables, Tech/ECA, 1993, ISBN 981-214-444-7</ref> |
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==Relationships to the Family of "BC" Devices== |
==Relationships to the Family of "BC" Devices== |
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{{Merge to|Pro Electron|date=April 2011}} |
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{{split section|BC series silicon transistors|date=March 2011}} |
{{split section|BC series silicon transistors|date=March 2011}} |
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The BC548 is a member of a larger group of similarly numbered transistors. |
The BC548 is a member of a larger group of similarly numbered transistors. Other part numbers have different characteristics and ratings. Its complement is the BC558. |
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⚫ | A family of older "BC" transistors predates the TO-92 BC54x series, the [[BC107]], [[BC108]] and [[BC109]], (with complements [[BC177]], [[BC178]] and [[BC179]]). These are generally housed in the [[TO-18]] metal package, the same as what the North American [[2N2222]] uses. These older transistors have similar characteristics as the TO-92 BC5xx devices and are electrically interchangeable. |
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The BC548 is flanked by two similar transistors, the [[BC547]] and the [[BC549]]. These are similar to the BC548 but the 547 has a greater V<sub>cbo</sub> of 50 volts and the 549 has the same V<sub>cbo</sub> of 30 volts but a lower noise figure. The 547 and 549 have complementary PNP versions numbered [[BC557|557]] and [[BC559|559]]. A [[BC556]] device also exists with a V<sub>cbo</sub> of 80 volts, which device finds extensive use in the [[current mirror]] input stages of medium quality [[audio amplifier]]s with relatively high rail voltages. |
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⚫ | A family of older "BC" transistors predates the TO-92 BC54x series, the [[BC107]], [[BC108]] and [[BC109]], (with complements [[BC177]], [[BC178]] and [[BC179]]). These are generally housed in the [[TO-18]] metal package, the same as what the North American [[2N2222]] uses. These older transistors have similar characteristics as the TO-92 BC5xx devices and are |
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The [[BC337]], [[BC338]] and [[BC339]] are a range of higher current, slower devices with complementary PNP versions [[BC327]], [[BC328]] and [[BC329]]. These are similar to the North American 2N2222 and [[2N2907]] in I<sub>c</sub> and f<sub>t</sub> values and have the same V<sub>cbo</sub> ratings as the BC547, 548 and 549. |
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The [[BC635]], [[BC637]] and [[BC639]] possess an I<sub>c</sub> value of 1 amp, a V<sub>cbo</sub> of between 45 and 80 volts and an f<sub>t</sub> of 50 to 130 MHz. These devices have a different lead configuration, with the collector lead in the middle. The complementary PNP versions are [[BC636]], [[BC638]] and [[BC640]]. |
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There are many other devices based on the BC54x family, such as the surface-mount versions of the BC547, 548 and 549; the [[BC847]], [[BC848]] and [[BC849]]. |
There are many other devices based on the BC54x family, such as the surface-mount versions of the BC547, 548 and 549; the [[BC847]], [[BC848]] and [[BC849]]. |
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==Historical Roots== |
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{{split section|OC series germanium transistors|date=March 2011}} |
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Before the [[silicon]] "BC" devices were developed, the older [[germanium]] technology "OC" series devices were used. These generally date between about 1958-1970. The most commonly encountered are the glass encapsulated OC44, OC45, OC71 and OC75. These were very low power devices with a V<sub>cbo</sub> generally in the 12-16 volt range and Ic values of less than 50 mA. The [[OC44]] and [[OC45]] were the first common British/European [[radio frequency]] devices with an f<sub>t</sub> around 1 MHz. The [[OC71]] and [[OC75]] were audio devices with an f<sub>t</sub> of about 150 kHz. A "power" version, the [[OC25]], with an I<sub>c</sub> of 3 Amperes was sometimes seen in a [[TO-3]] package. All of these earlier [[germanium transistors]] were generally PNP, although NPN versions were made. These older germanium devices contained [[indium]], a metal with a very low melting point which limited the power dissipation of the devices to a very low level and rendered them unreliable in harsh environments, such as use in aircraft where wide temperature variations are encountered. The silicon technology based "BC" devices appeared and superseded the older germanium based devices. The doped silicon from which the newer devices were fabricated could withstand much greater temperature variations and allowed much greater power dissipations. The main limiting factor of the newer silicon [[BJT]]s was [[thermal runaway]], a condition where the current gain ("beta") of a BJT increases as it gets hotter. This increases the collector current (I<sub>c</sub>) despite the base current being constant. An increase in I<sub>c</sub> makes the chip "die" hotter, increasing the "beta" and thus I<sub>c</sub>, and so on until the transistor is cooled externally or it burns out. This [[thermal runaway]] can be overcome by using an emitter resistor in combination with a voltage divider providing the base bias current, or by using a resistor between the collector and the base (sliding bias), we call all these measures against [[thermal runaway]] [[bipolar transistor biasing]]. |
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==References== |
==References== |
Revision as of 03:31, 4 April 2011
The BC548 is a general purpose silicon NPN BJT transistor found commonly in European electronic equipment.
If the TO-92 package is held in front of one's face with the flat side facing toward you and the leads downward, (see picture) the order of the leads, from left to right is collector, base, emitter.
Specifications
The exact specs of a given device depend on the manufacturer. It is important to check the datasheet for the exact device and brand you are dealing with. Philips and Telefunken are two manufacturers of the BC548.
Relationships to the Family of "BC" Devices
The BC548 is a member of a larger group of similarly numbered transistors. Other part numbers have different characteristics and ratings. Its complement is the BC558.
A family of older "BC" transistors predates the TO-92 BC54x series, the BC107, BC108 and BC109, (with complements BC177, BC178 and BC179). These are generally housed in the TO-18 metal package, the same as what the North American 2N2222 uses. These older transistors have similar characteristics as the TO-92 BC5xx devices and are electrically interchangeable.
There are many other devices based on the BC54x family, such as the surface-mount versions of the BC547, 548 and 549; the BC847, BC848 and BC849.
References
- ^ World's Transistor Comparison Tables, Tech/ECA, 1993, ISBN 981-214-444-7