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[Moved] Operation of a transistor

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Liamlambchop

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Hey guys,

I have posted this elsewhere on the forum, but it wasn't in the correct category. I thought I might have better luck here!

Out of interest I tried to explain how, in a physicists terms, a transistor works. Below is what I came up with.

" For an NPN transistor: There are more excess electrons in a single the N layer of the NPN transistor than there are holes in the P layer - the P layer is very thin compared with an N layer. At 0.7V the Vbe is sufficient to cause the holes of the base to be filled by electrons from the emitter. This closes the depletion zone, and hence allows the rest of the emitter excess electrons to travel to the collector under the influence of Vce. Current is now flowing through the transistor. "

Is this correct?
 

Liamlambchop

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I did do some reading to come up with the above explanation... Are you implying that I need to do some further reading?

Nice profile photo btw :))) You must be a good person to ask about transistors!!
 

goldsmith

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Dear Liamlambchop
Again Hi
If the BE junction be forward bias , the voltage of CE should be about : C=+v ( higher than be ) and emitter , ground .( for the npn transistor). thus the BE junction will be short circuit ( approx ) ( that called that the be is conducted) . thus the ce junction will be short circuit ( approx) . see tom floyd book , please , it has more colour photos , that can help you.
Best Things
Goldsmith
 

subbuindia

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Hi friend......

Transistor is an electronic device, the name itself TRANSfer of resISTOR i.e., the transfer of current or voltage from high resistance to low resistane. (TRANSISTOR= TRANSfer+ resiSTOR).

Coming to its construction, transistor has three plates or terminals namely emitter, collector, base.
Emitter: Moderate size and heavily doped
Base: Small size and less doped
Collector: Big size and moderately doped
Transistor has two junctions namely Base-Emitter junction and Base-collector junction.


For NPN transistors, electrons are majority carriers and holes are minority carriers
For PNP transistors, holes are majority carriers and electrons are minority carriers

http://media-1.web.britannica.com/eb-media/28/76428-004-57D480F6.gif
http://www.radartutorial.eu/21.semiconductors/pic/transistor9.en.jpg


Coming to its operation, I consider NPN transistor shown in above figures. If I apply forward bias to Base-emitter junction and reverse operation to Base-collector junction. Then majority carriers in the N-region i.e., holes are moving towards base from emitter, reach to base due to repulsion. But, base is lightly doped hence few number of electrons combined with holes that are present in base. And remaining electrons are moving towards collector which already in reverse bias hence large current flows through the load means that high voltage is developed at the output. Hence, in this situation transistor act as amplifier.

See the following link for more details with neat explanation.

Transistor Operating Details

Hope, You got it....
 
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