Bipolar junction transistor

A bipolar junction transistor (BJT or bipolar transistor) is a type of transistor that relies on the contact of two types of semiconductor in order for it to work. BJTs can be used as amplifiers, switches, or in oscillators. BJTs can be found either on their own, or in large numbers as parts of integrated circuits.

They are named bipolar transistors because their operation involves both electrons and holes.

The current gained is measured in h_fe, Forward Current Gain. Typical amount can be between 200-350.

Bipolar Junction Transistor Media

• 

  The picture shows ths symbol of Bipolar Junction transistor : PNP type and NPN type.

• 

  3D model of a TO-92 package, commonly used for small bipolar transistors

• 

  NPN BJT with forward-biased B–E junction and reverse-biased B–C junction

• 

  Simplified cross section of a planar NPN bipolar junction transistor

• 

  Die of a 2N2222 NPN transistor: the NPN materials are made in layers with the collector at the bottom. Bond wires connect metalization on the base to the left lead, and emitter to the right. The collector is connected to the can with a third external lead.

• 

  Symbol for NPN bipolar transistor with current flow direction

• 

  Structure and use of NPN transistor; arrow according to schematic

• 

  Band diagram for NPN transistor at equilibrium

• 

  Band diagram for NPN transistor in active mode, showing injection of electrons from emitter to base, and their overshoot into the collector

• Error creating thumbnail: About to transcode 1 SVG file(s)

  Converting Ebers-Moll_model_schematic_(NPN).svg to /var/www/html/w/images/temp/transform_55f1aa1d6ec1.png ... org.apache.batik.transcoder.TranscoderException: null Enclosed Exception: Content is not allowed in prolog. at org.apache.batik.transcoder.XMLAbstractTranscoder.transcode(XMLAbstractTranscoder.java:136) at org.apache.batik.transcoder.SVGAbstractTranscoder.transcode(SVGAbstractTranscoder.java:158) at org.apache.batik.apps.rasterizer.SVGConverter.transcode(SVGConverter.java:1008) at org.apache.batik.apps.rasterizer.SVGConverter.execute(SVGConverter.java:719) at org.apache.batik.apps.rasterizer.Main.execute(Main.java:956) at org.apache.batik.apps.rasterizer.Main.main(Main.java:1009) Caused by: org.apache.batik.dom.util.SAXIOException: Content is not allowed in prolog. at org.apache.batik.dom.util.SAXDocumentFactory.createDocument(SAXDocumentFactory.java:459) at org.apache.batik.dom.util.SAXDocumentFactory.createDocument(SAXDocumentFactory.java:357) at org.apache.batik.anim.dom.SAXSVGDocumentFactory.createDocument(SAXSVGDocumentFactory.java:203) at org.apache.batik.anim.dom.SAXSVGDocumentFactory.createDocument(SAXSVGDocumentFactory.java:283) at org.apache.batik.transcoder.XMLAbstractTranscoder.transcode(XMLAbstractTranscoder.java:129) ... 5 more Caused by: org.xml.sax.SAXParseException; systemId: file:/var/www/html/w/images/temp/svg_3823d5d8f14917d899cbb586/Ebers-Moll_model_schematic_(NPN).svg; lineNumber: 2; columnNumber: 1; Content is not allowed in prolog. at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:204) at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:178) at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:399) at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:326) at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1466) at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:993) at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:601) at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:112) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:504) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770) at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141) at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213) at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:642) at org.apache.batik.dom.util.SAXDocumentFactory.createDocument(SAXDocumentFactory.java:453) ... 9 more ... error (SVGConverter.error.while.rasterizing.file)

  Ebers–Moll model for an NPN transistor. IB, IC and IE are the base, collector and emitter currents; ICD and IED are the collector and emitter diode currents; αF and αR are the forward and reverse common-base current gains.

Other websites

• Simulation of a BJT in the Common Emitter Circuit Archived 2010-07-16 at the Wayback Machine