The Physics of the Transistor
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The Physics of the Transistor Jim Royston Electronic Engineering La Trobe University
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The Physics of the Transistor. Jim Royston Electronic Engineering La Trobe University. The B-E junction is forward biased and the C-B junction is reverse biased. - PowerPoint PPT Presentation
Transcript of The Physics of the Transistor
The Physics of the Transistor
Jim RoystonElectronic Engineering
La Trobe University
• The B-E junction is forward biased and the C-B junction is reverse biased.
• There is an exponential relationship between the thickness of the B-E depletion region and the current of electrons "injected" into the base as minority carriers.
T
BESC V
VII exp
• The base region is very thin and has a lower doping than the emitter or collector.
• The profile of concentration of minority carriers (electrons in an NPN transistor) in the base is linear.
• The amplifying action is produced by transferring a current from a low-resistance circuit to a high resistance circuit.
• transfer + resistor → transistor
• The C-B junction has a reverse bias leakage current ICBO which is typically microamps or nanoamps, and can be neglected unless temperature effects are important.
• Approximately, ICEO ≈ β ICBO but both currents are small.
• There is an injection of holes into the emitter, where they are minority carriers, from the base – this can be kept small by heavily doping the emitter with donor impurities.
Gray, P. R. & Meyer, R. G., "Analysis & Design of Analog Integrated Circuits", 3rd edition 1993, New York, John Wiley & Sons.
References
• William Beaty "How Do Transistors Work?" 1995 http://amasci.com/amateur/transis.html
• Wikipedia "Bipolar Junction Transistors" accessed 2007 http://en.wikipedia.org/wiki/Bjt
• Gray, P. R. & Meyer, R. G., "Analysis & Design of Analog Integrated Circuits", 3rd edition 1993, New York, John Wiley & Sons.
• Bogart, T. F. et al, "Electronic Devices & Circuits", 3rd edition 2001, Upper Saddle River, New Jersey, Prentice-Hall (Pearson).
• Boylestad, R. L. & Nashelsky, L., "Electronic Devices and Circuit Theory", 8th edition 2003, Upper Saddle River, New Jersey, Prentice-Hall (Pearson).
