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How a pn junction amplify any signal in transistors?

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Electo_tada

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transistorworking

A very simple question is how a pn junction amplify any signal ?
Please answer in very basic terms and analogies.

Thanks!
 

Re: Transistor working ?

Consier it this way :
a transistor is basically two diodes joined back to back. Right ? When working as an amplifier ,biased one of the diode is forward biased whereas the other reverse biased.

As first one is forward biased it conducts and a current flow through a low resistance region ( Forward biased ).
But current can't go anywhere but though other diode which is reverse biased. hence now same little current flows through a very high resistance region.

This low current multiplied by high R results in V= I(low) R(very high)
hence Vout becomes much higher than Vin.

Thanks
 
Re: Transistor working ?

Open with DJVU browser or a plug-in. It is a 2 pages about basic transistor properties. Very good!
 

Re: Transistor working ?

You can see a transistor as avariable resistor if you try to use it in tryode zone(amplifier). current flowing in transistor's base(driven by low voltage and low current) is like cursor. higher current willreduce voltage drop between collector and emitter.
for example if base is driven by a signal from 0 to 5V you can find 0,2 to 50V between emitter and collector if you supply collector with 50 V and emitter in connected to ground.

if you like hydraulic examples, a transistor can be seen as a water tap. and base current is the torque you use to turn it on.

ask if you don't undertand something.
 

Re: Transistor working ?

truebs said:
Consier it this way :
a transistor is basically two diodes joined back to back. Right ? When working as an amplifier ,biased one of the diode is forward biased whereas the other reverse biased.

As first one is forward biased it conducts and a current flow through a low resistance region ( Forward biased ).
But current can't go anywhere but though other diode which is reverse biased. hence now same little current flows through a very high resistance region.

This low current multiplied by high R results in V= I(low) R(very high)
hence Vout becomes much higher than Vin.

Thanks
Click to expand...

Just want to add onething here.

The word Transistor means "transfer resistor". Thus, this is how it amplify a signal from low resistance to high resistance as explained earlier by truebs.
 

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