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Topic: Bipolar junction transistor

	Transistor (Site not responding. Last check: 2007-11-06)
		The bipolar transistor, composed of two closely coupled P-N junctions, is bipolar in that both electrons and holes are involved in the conduction process.
		A bipolar transistor has base, emitter and collector electrodes, and is a current-controlled device (able to deliver a change in output voltage in response to a change in input current) with a low input impedance.
		In the bipolar transistor (as in all modern transistors), the vital junctions between the N-type and P-type layers are buried deep within the semiconductor crystal where they cannot be affected by their surroundings.
	encyclobeamia.solarbotics.net /articles/transistor.html (684 words)

	Online Encyclopedia and Dictionary - Bipolar junction transistor
		A bipolar junction transistor (BJT) is a type of transistor, an amplifying or switching device constructed of doped semiconductor.
		In normal operation, the emitter-base junction is forward biased and the base-collector junction is reverse biased.
		The germanium transistor was more common in the 1950s and 1960s, and while it exhibits a lower "cut off" voltage, making it more suitable for some applications, it also has a greater tendency to exhibit thermal runaway.
	fact-archive.com /encyclopedia/P-n-p_transistor (743 words)

	Bipolar junction transistor (Site not responding. Last check: 2007-11-06)
		Bipolar transistors are made from 3 sections of semiconductor material (alternating P-type and N-type), with 2 resulting P-N junctions.
		Bipolar transistors are classified as either NPN or PNP according to the arrangement of their N-type and P-type materials.
		Note that the bipolar transistor is a current-amplifying device, unlike the vacuum tube and the field-effect transistor (FET), both of which depend upon voltage changes to operate.
	encyclobeamia.solarbotics.net /articles/bip_junct_trans.html (783 words)

	Bipolar junction transistor: Definition and Links by Encyclopedian.com
		A Bipolar Junction Transistor, (BJT), is a type of transistor, an amplifying or switching device constructed of doped semiconductor.
		A bipolar transistor is a sandwich of differently doped sections, either NPN or PNP.
		In normal operation, the emitter-base junction is forward biased and the base-collector junction is reverse biased.
	www.encyclopedian.com /bi/Bipolar-junction-transistor.html (452 words)

	Transistor
		The transistor is an arrangement of semiconductor materials that share common physical boundaries.
		The transistor action is such that if the electric potentials on the segments are properly determined, a small current between the base and emitter connections results in a large current between the emitter and collector connections, thus producing current amplification.
		The p-n-p junction transistor, consisting of a thin layer of n-type semiconductor lying between two p-type semiconductors, works in the same manner, except that all polarities are reversed.
	www.mtmi.vu.lt /pfk/funkc_dariniai/transistor/index.html (1073 words)

	ipedia.com: Transistor Article (Site not responding. Last check: 2007-11-06)
		Transistor was also the common name in the sixties for a transistor radio, a pocket-sized portable radio that utilized transistors (rather than vacuum tubes) as its active electronics.
		The transistor is considered by many to be one of the greatest discoveries or inventions in modern history, ranking with banking and the printing press.
		In bipolar transistors, the semiconductor is formed into structures called p-n junctions that allow electricity to flow in only one direction through them – that is, they are a conductor when voltage is applied in one direction, and an insulator when it is applied in the other direction.
	www.ipedia.com /transistor.html (4761 words)

	Engineering Database
		A method of biasing a Bipolar Junction Transistor in which the bias voltage is supplied to the base by means of a resistor.
		In a JFET device the gate formsa true semiconductor junction with the channel, while in a MOSFET device the gate isinsulated from the channel by a very thin (typically less than the wavelength of light)layer of glass (silicon dioxide) and the gate is either metal or doped silicon(polysilicon), hence the acronym metal-oxide semiconductor.
		In a bipolar junction transistor, the condition when the emitter to collector voltage is less than the emitter to base voltage.
	www.diracdelta.co.uk /science/source/t/r/transistor/source.html (942 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		When a tiny current is forced into the base of the bipolar junction transistor, it creates a much larger current flow from the collector to the emitter, through the base.
		The upper frequency limit of transistors operating in conventional regimes is limited by the transit time of carriers under the gate, for a field effect transistor, or across the base and collector depletion region, for a bipolar junction transistor.
		Bipolar junction transistors a bipolar transistor uses a small current to control a larger current, a little like a relay.
	www.lycos.com /info/bipolar-junction-transistor--base.html (564 words)

	The Bipolar Transistor; NPN and PNP Transistors
		The bipolar transistor is a three-terminal device consisting of 3 layers of alternating n- and p-type materials referred to as the emitter, base, and collector.
		In the NPN transistor, the base is composed of a p-type material and is sandwiched by an n-type emitter and an n-type collector.
		The base-emitter junction of a transistor in active region is forward-biased while its base-collector junction is reverse-biased.
	www.ecelab.com /bipolar-transistor.htm (419 words)

	BJT: Bipolar junction transistor (Site not responding. Last check: 2007-11-06)
		The bipolar junction transistor (BJT) was the first type of transistor to be commercially mass-produced.
		Bipolar transistors are so named because the main conduction channel uses both electrons and holes to carry the main electric current.
		When the BJT is not powered, the junctions are in unbiased thermal equilibrium with a depletion region formed at each junction.
	www.javvin.com /hardware/BJT.html (69 words)

	Semiconductor OneSource: Semiconductor Glossary -- Search For : transistor
		Junction Field Effect Transistor; field effect transistor in which channel and its conductivity is controlled by changing width of the space charge region associated with a p-n junction.
		bipolar transistor in which current flows across the base in the direction parallel to the wafer surface; in contrast to conventional vertical bipolar transistor in which current across the base flows in the direction normal to the surface; l.t.
		bipolar transistor in which current across emitter-base and collector-base junctions flows in the direction normal to the wafer surface; conventional configuration as opposed to lateral transistor which features inferior characteristics.
	semiconductorglossary.com /default.asp?searchterm=transistor (1350 words)

	Meter check of a transistor : BIPOLAR JUNCTION TRANSISTORS (Site not responding. Last check: 2007-11-06)
		Bipolar transistors are constructed of a three-layer semiconductor "sandwich," either PNP or NPN.
		All bipolar transistors have three wires, of course, but the positions of the three wires on the actual physical package are not arranged in any universal, standardized order.
		However, when the base-emitter junction is forward biased by the controlling signal, the normally-blocking action of the base-collector junction is overridden and current is permitted through the collector, despite the fact that electrons are going the "wrong way" through that PN junction.
	www.allaboutcircuits.com /vol_3/chpt_4/3.html (1390 words)

	Bipolar Junction Transistors (BJT)
		The general operation of a transistor is as a variable resistor with the base terminal of the transistor functioning as the controlling input.
		The BJT must be properly biased with a forward bias on the base-emitter junction and a reverse bias on the base-collector junction.
		For the PNP transistor, the voltage potential of the emitter must be more positive than the voltage potential of the base to forward bias the base-emitter junction.
	www.hcc.hawaii.edu /~sdunan/cent112/notes/06FTransistors (1991 words)

	Radio-Electronics.Com :: Bipolar Junction Transistor (BJT)
		The bipolar transistor dates back to the middle of the twentieth century when three scientists named Bardeen, Brattain, and Shockley working at Bell Laboratories in the USA discovered it.
		When the base emitter junction is forward biased the electrons move from the n-type region towards the p-type region and the holes move towards the n-type region.
		When the junction is reverse biased the holes and electrons move away from one another resulting in a depletion region between the two areas and no current flows.
	www.radio-electronics.com /info/data/semicond/bjt/bipolar_junction_transistor.php (930 words)

	Bipolar Junction Transistor (BJT)
		In an npn transistor, a thin and lightly doped p-type material is sandwiched between two thicker n-type materials; while in a pnp transistor, a thin and lightly doped n-type material is sandwiched between two thicker p-type materials.
		In many schematics of transistor circuits (especially when there exist a large number of transistors in the circuit), the circle in the symbol of a transistor is omitted.
		The three terminals of a transistor are typically used as the input, output and the common terminal of both input and output.
	fourier.eng.hmc.edu /e84/lectures/ch4/node3.html (374 words)

	[No title]
		The development of the transistor was the greatest single advancement in electronics since the development of the vacuum tube in the early part of the 20th century.
		BJT switches are used whenever a device such as a microprocessor needs to switch the current to any device which draws more current than the microprocessor can supply.
		Transistor parameters may be found in a data sheet for the particular transistor or in a transistor data book.
	www.angelfire.com /planet/funwithtransistors/Basics_04_BJT.html (7580 words)

	Current Mirrors - Bipolar Junction Transistors
		An interesting and often-used circuit applying the bipolar junction transistor is the so-called current mirror, which serves as a simple current regulator, supplying nearly constant current to a load over a wide range of load resistances.
		Remember, the transistor's collector current is almost equal to its emitter current, as the α ratio of a typical transistor is almost unity (1).
		Transistors in a current mirror circuit must be maintained at the same temperature for precise operation.
	www.opamp-electronics.com /tutorials/current_mirror_3_04_12.htm (958 words)

	Bipolar junction exhibiting suppressed kirk effect - US Patent 5336926 (Site not responding. Last check: 2007-11-06)
		One of the common problems associated with the standard bipolar junction transistor is that the performance of the device is limited at high current densities.
		Therefore, what is needed is a bipolar junction transistor capable of suppressing the Kirk Effect to allow much higher current densities than achievable under prior art approaches.
		A bipolar transistor comprising emitter, base, and collector regions is described wherein numerous specific details are set forth, such as specific doping levels, processing steps, dimensions, etc., in order to provide a thorough understanding of the present invention.
	www.patentstorm.us /patents/5336926-description.html (4284 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		The BJT dominated the market initially but now most of the transistors, particularly in integrated circuits, are of the MOS type.
		While most transistors of any type are made today as elements of integrated circuits (ICs), which can contain millions of circuit elements, single or discrete transistors are still useful in many applications like high frequency or power units.
		Those points in a gate circuit marked by the label "Vcc" are all connected to the same point, and that point is the positive terminal of a DC voltage source, usually 5 volts.
	www.lycos.com /info/bipolar-junction-transistor--miscellaneous.html (412 words)

	Lessons In Electric Circuits -- Volume III (Semiconductors) - Chapter 5
		In a junction field-effect transistor, or JFET, the controlled current passes from source to drain, or from drain to source as the case may be.
		Unlike the bipolar junction transistor where the emitter is clearly distinguished from the collector by the arrowhead, a JFET's source and drain lines both run perpendicular into the bar representing the semiconductor channel.
		In the first BJT simulation of chapter 4, a constant-current source of 20 µA was used for the controlling signal, but remember that a JFET is a voltage-controlled device, not a current-controlled device like the bipolar junction transistor.
	www.ibiblio.org /obp/electricCircuits/Semi/SEMI_5.html (3461 words)

	Bipolar Junction Transistors
		A Bipolar Transistor essentially consists of a pair of PN Junction Diodes that are joined back-to-back.
		The development of a planar process yielded the first circuits on a chip and for a decade, bipolar transistor operational amplifiers and digital TTL circuits were the workhorses of any circuit designer.
		The structure of an NPN bipolar transistor is shown in Figure 1 (a).
	www.mtmi.vu.lt /pfk/funkc_dariniai/transistor/bipolar_transistor.htm (3554 words)

	Transistor \| World of Computer Science
		A transistor consists of a piece semiconducting crystal (usually silicon, but sometimes germanium or gallium arsenide) with which impurities such as antimony, bismuth, arsenic, and phosphorous have been mixed by a process called doping.
		Until the invention of the transistor in 1947, digital circuits were composed of vacuum tubes, which also function as valves for current flow.
		Although discrete transistors are still used, the vast majority of transistors are built into integrated circuits as parts of microprocessors, memory chips, and the like.
	www.bookrags.com /research/transistor-wcs (1209 words)

	Bipolar Junction Transistors
		The ideal transistor model is based on the ideal p-n diode model and provides a first-order calculation of the dc parameters of a bipolar junction transistor.
		The discussion of the ideal transistor starts with a discussion of the forward active mode of operation, followed by a general description of the four different bias modes, the corresponding Ebers-Moll model and a calculation of the collector-emitter voltage when the device is biased in saturation.
		The minority-carrier distribution in the quasi-neutral regions of the bipolar transistor, as shown in Figure 5.3.1, is used to analyze this situation in more detail.
	ece-www.colorado.edu /~bart/book/book/chapter5/ch5_3.htm (1583 words)

	Bipolar Junction Transistors (Site not responding. Last check: 2007-11-06)
		The development of a planar process yielded the first circuits on a chip and for a decade, bipolar transistor operational amplifiers, like the 741, and digital TTL circuits were the workhorses of any circuit designer.
		Nevertheless, bipolar transistors remain important devices for ultra-high-speed discrete logic circuits such as emitter coupled logic (ECL), power-switching applications and in microwave power amplifiers.
		We then present the ideal transistor model and derive an expression for the current gain in the forward active mode of operation.
	physics.ship.edu /~mrc/pfs/308/semicon_book/book/chapter5/ch5_1.htm (319 words)

	Transistors
		A bipolar junction transistor consists of three regions of doped semiconductors.
		Part of the manufacturer's data for transistors is a set of maximum values which must not be exceeded in its operation.
		These form some of the constraints on transistor operation which are a part of the design of any circuit.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/trans.html (214 words)

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