![]() This is why the emitter current is equal to the sum of the base and collector currents. A very small base current also flows through the device as a result of this movement. The electrons begin to move towards the collector as recombined holes and electrons become separated from one another. As a result, these electrons are now collected at the transistor’s collector terminal. Because of the strong electrostatic field, electrons begin to drift at the collector region due to the very thin base region and the reverse voltage at the collector-base junction. As a result, only a few electrons combine with the holes once they reach their destination. ![]() The following diagram depicts the biased condition of an NPN transistor:Ĭharger Carrier Movement in an NPN Transistorīecause the base region is very thin and doped lightly. These two depletion regions serve as a potential stumbling block to any further majority carrier flow. This is why the depletion width at the collector-base junction is wider than at the emitter-base junction. To put it another way, in the case of a lightly doped region, the width of the depletion region will be greater than in the case of a highly doped region. It’s worth noting that the thickness or thinness of the depletion region is determined by the material’s doping concentration. Similarly, a depletion region forms at the transistor’s base-collector junction after a period of time. Only about 5% of electrons combine with holes in this region after reaching the base region, while the rest drift across the collector region. However, a depletion region forms at the transistor’s emitter-base junction after a certain amount of time has passed. A transistor is made up of two PN junctions, as we already know.Īs a result, under no biased conditions, electrons in the emitter region begin to move towards the base region due to temperature variations. We’ve already talked about how a PN junction diode works in the absence of bias. It is then referred to as the transistor’s unbiased state. When there is no applied bias to the transistor or when there is no battery connected between its terminals. The reason for this is that the collector region’s thickness is slightly greater than the emitter region. It’s worth noting that the emitter and collector regions cannot be switched around. Its inverse is the PNP transistor, which has a P-region sandwiched between two N-Type regions. And the collector region’s doping level is moderate, falling somewhere between the emitter and the base region. ![]() The emitter region has a lot of doping, while the base region also has a lot of doping. The levels of doping in each of the three regions are different. It functions as two PN junction diodes due to the presence of two junctions in between three regions. The collector-base junction, on the other hand, is the point where the base and collector regions meet. The emitter-base junction is the region that connects the emitter and the base region. It is divided into three sections: emitter, base, and collector. The NPN transistor is made up of a number of different components.
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