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Purpose of NPN transistor


Munky
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http://www.satcure-focus.com/tutor/page4.htm
http://www.physlink.com/Education/AskExperts/ae430.cfm

Hi Munky!

sorry  i can't provide you with my own explanation..
try those links.. hope they help you.. if you need more explanation, google it up! im sure you'll find some simple explanations there.. GOod luck!

BTW, Welcome to eLab!  ;D  8)

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  • 2 weeks later...

A npn transistor works jus like a silinode. Imagine the base being the silinoide
activator and the collector is the hot wire and the emiter is the part that get
connected when the silinoide gets turned on.  The Base also controls the
amount of power that is allowed to pass through.

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  • 1 month later...

I think, In amplifiers the NPN Transistors work on the negative frequencies and the PNP transistors work on the Postive Frequencies, this is only an example used in amplifiers though.

Nope.
All transistors in an amplifier amplify all frequencies. Frequencies don't have polarity.

If the amplifier has a complimentary class AB push-pull output and has a positive and a negative supply, then the NPN is an emitter-follower for the positive output voltage swing and the PNP is an emitter-follower for the negative output voltage swing. 
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To understand how "they" work, you really need to understand semi-conductor physics including electron bonding at the atomic level. Once you get "that stuff down", terms like... doping levels, majority and minority carriers, etc. will make a bit more sense and you'll know exactly how they work.

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A NPN transistor works on the basis of semiconductor theory ie current given to the emitter (N Region) is the sum of base current (P Region)+collector current(N Region).in power mode use of NPN transistor when the base gets +ve voltage(low current) -ve voltage from emitter jumps to collector.In amplifying mode signals feed in emiitor-base region jumps to collector-base region if we include a battery source in collector circuit we can get an amplified output.

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...in power mode use of NPN transistor when the base gets +ve voltage(low current) -ve voltage from emitter jumps to collector.In amplifying mode signals feed in emiitor-base region jumps to collector-base region...



Voltages "jump"???? While electrons may "jump" from valence to valence, can you please explain the theory of "-ve voltage jumping" from emitter to collector???
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Sorry physics sir,i am only a student also do not know much about transistor theory.But in practical use of transistor no one thinks of theory.I just used the term 'jump' just to explain its working for practical circuit designing,a simple example is switching a relay 'on' using npn transistor in conjunction with IC MCT2E.('+'ve voltage from IC MCT2E is feed to base of npn transistor and '-'ve voltage from emittor of npn get transferred to collector which then powers the relay).

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Here is one way to look at transistors..........

Consider a large, tall water tower with a faucet on the side. For a NPN, the water tower is the collector voltage the faucet handle is the base, and the what comes out of the faucet is the emitter. The more you open the faucet (provide more base current) the more comes out (emitter current). Also, the more you open the faucet the lower the pressure differential between faucet inlet and outlet (lower Vce sat). If the water tower side pressure becomes too high, the faucet will fail (collecter voltage to high and transistor goes up in smoke)... etc. etc.

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