As shown in Figure below, transistors have two junctions, one between the emitter and the base, called the Base Diodes – emitter, and the other between the collector and the base, called the Base Diodes – Collector. Since each diode has 2 possible bias, the bias Manu (forward biased) and bias backwards (reverse biased), the transistor has 4 (four) the possibility of bias. Possible bias each diode is shown in the table below
Bloc Diagrams, Schematic and Symbol Transistor NPN
Possible bias base-emitter diode and the base-collector
If both diodes (Diodes Diode emitter and collector) by bias forward, then both diodes will conduct a sizeable current. Likewise, if the second diode bias given backwards, then only a very small current, if not downright not happen currents, through both dioa. Both this bias, does not produce enough characteristics interesting to discuss. The discussion will begin exciting, if diberiprategangan emitter diodes and diode forward bias current collector is given backwards (so-called bias Forward-Backward), as tampat in Figure below.
Forward-Backward bias transistors
From the picture above, it appears that the diode is forward biased emitter given by V BE and diode bias current collector is given back by V CB.
Due to differences in the concentration of doping in the emitter and base regions, the electrons from the VBE diijeksikan (emitted) from the emitter to the base, resulting in emitter currents, IE. Then, since the base area didop with very little concentration and have a structure that is very thin, only very few electrons that fall into the area that produces the flow Base Base, IB, so that most of the electrons is passed continuously to the collector region.
Collectors will collect (collected) electrons toward him, and moved him to a voltage V CB, resulting in a flow collector, IC. The circuit appears on the image above to unite the voltage at the base terminal, so that known as Allied Base (Common Base). The magnitudes of the resulting current, IE, IB and IC, can be illustrated in the Figure below. However, this series can not show you an interesting process, where there is no relationship can be inferred. Thus, this circuit is rarely used in practice.
The current in the circuit direction Base Allied (Common Base)