Front concepts:
Concept forward biased and reverse biased;
Then the positive P-type semiconductor, N-type semiconductor connected to the negative electrode; referred to as a forward-biased;
Otherwise known as the reverse bias;
Transistor is the most important one active device;
It amplifies the input signal to produce an output signal larger than the input, the output signal of course, increased power from the external power supply transistor circuit;
Similar resistance or capacitive devices such passive step-up transformer having a voltage gain not only the power gain;
Power gain device: some feedback from the output terminal an output signal to an input of a class may form an oscillator;
The transistor is a very effective interface circuit may be applied between the IC and other circuits, or between a sub-circuit and the other sub-circuit.
Transistor model - current amplifier
Note that, the current Ic is amplified, not because the through BC diode conduction caused between the opposite Vbc is reverse biased, that come from Ic, can be seen as causing a temporary effect transistor.
Transistor operation three states:
1. The emitter junction is forward biased collector junction reverse biased, work in the enlarged region;
2. emitter junction is forward biased, the collector junction forward biased in the saturation region;
3. emitter junction reverse biased collector junction reverse biased, ending work area;
