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close this bookAmplifier Teaching Aid (GTZ, DED; 86 pages)
View the documentPreface
View the documentIntroduction
Open this folder and view contentsLesson 1 - Semiconductor Review
close this folderLesson 2 - Bipolar Transistor
close this folderLesson Plan
View the documentIntroduction
View the documentTransistor structures and symbols
View the documentTransistor currents
View the documentCurrent gain
View the documentTransistor connections
View the documentWorksheet No. 2
View the documentExperiment No. 2
Open this folder and view contentsBipolar Transistor II
View the documentFirst Evaluation
Open this folder and view contentsLesson 4 - Transistor Fundamentals
Open this folder and view contentsLesson 5 - Transistor Biasing
Open this folder and view contentsLesson 6 - Transistor Biasing II
View the documentSecond Evaluation
Open this folder and view contentsLesson 7 - Small Signal Amplifier
Open this folder and view contentsLesson 8 - Small Signal Amplifier II
Open this folder and view contentsLesson 9 - Small Signal Amplifier III
Open this folder and view contentsLesson 10 - Large Signal Amplifier
View the documentThird Evaluation
 

Transistor currents

(see Fig. 2-4)

VBB forward biases the emitter diode, forcing the free electrons in the emitter to enter the base. The thin and lightly doped base gives almost all these electrons enough time to diffuse into the collector. These electrons flow through the collector, through RC, and into the positive terminal of the VCC voltage source. In most transistors, more than 95% of the emitter electrons flow to the collector, less than 5% flow out the external base lead.


Fig. 2-4: NPN Transistor

Recall Kirchhoff's current law:

=> IE = IC + IB


Fig. 2-5: Transistor currents

Because IB is very small, for circuit analysis, we can do the following approximation:

IC is equal to IE
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