ch20 - ECE3500SemiconductorMaterials andDevices

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    Topic 20 : Bipolar Junction Transistors -                 Principles of Operation and                 Active Mode Biasing                       Fall 2007 ECE 3500 - Semiconductor Materials  and Devices
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    Learning Objectives In this topic you will learn: The physical operation of a BJT. How to design a high gain BJT. How to calculate the emitter, base and  collector currents flowing in a symmetric  BJT (of uniform cross-sectional area) in  the active mode of biasing.
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    Bipolar Junction Transistor The bipolar junction transistor is a three-terminal   device in which the  collector-to-emitter current is  controlled by the base current, i.e. it  behaves as a  current-controlled  current source .   As mentioned earlier, control  functions (e.g.  amplification ) are  possible with three-terminal devices.
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    Fundamental Operation of BJT Recall that in a reverse-biased p-n junction under illumination, the current flowing is directly proportional to the  generation rate  of e - -h +  pairs.  In the BJT the current flowing through the reverse-biased collector-base junction is proportional to the  injection rate   of e - s/h + s from the forward biased emitter-base junction.
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    Fundamental Operation of BJT (cont’d)
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    Fundamental Operation of BJT (cont’d)
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  Requirements for a “Good” BJT For a “good” transistor (one with  high gain) we must have the
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This note was uploaded on 03/11/2010 for the course ECE 4350 taught by Professor Singh during the Spring '07 term at Villanova.

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ch20 - ECE3500SemiconductorMaterials andDevices

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