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p–n junctions represent the simplest case of a semiconductor electronic device; a p-n junction by itself, when connected on both sides to a circuit, is a diode. More complex circuit components can be created by further combinations of p-type and n-type semiconductors; for example, the bipolar junction transistor (BJT) is a semiconductor in ...
Band-bending diagram for p–n diode in forward bias. Diffusion drives carriers across the junction. Quasi-Fermi levels and carrier densities in forward biased p–n-diode. The figure assumes recombination is confined to the regions where majority carrier concentration is near the bulk values, which is not accurate when recombination-generation ...
This applied voltage causes the lower p–n junction to become forward biased, allowing a flow of electrons from the emitter into the base. In active mode, the electric field existing between base and collector (caused by V CE ) will cause the majority of these electrons to cross the upper p–n junction into the collector to form the collector ...
A PN junction in forward bias mode, the depletion width decreases. Both p and n junctions are doped at a 1e15/cm3 doping level, leading to built-in potential of ~0.59V. Observe the different Quasi Fermi levels for conduction band and valence band in n and p regions (red curves). A depletion region forms instantaneously across a p–n junction.
Band diagram for p–n junction at equilibrium. The depletion region is shaded. φ B denotes band shift for holes and charges level. See P–n diode. The inner workings of a light emitting diode, showing circuit (top) and band diagram when a bias voltage is applied (bottom).
The model of a forward biased pn junction having an approximately constant 0.7V is also a much used approximation for transistor base-emitter junction voltage in amplifier design. The piecewise method is similar to the small signal method in that linear network analysis techniques can only be applied if the signal stays within certain bounds.
p–n junction operation in forward bias mode showing reducing depletion width. Both p and n junctions are doped at a 10 15 /cm 3 doping level, leading to built-in potential of ~ 0.59 V. Observe the different quasi-fermi levels for conduction band and valence band in n and p regions (red curves).
When a split supply (dual power supply) is available, this biasing circuit is the most effective. It provides zero bias voltage at the emitter or collector for load. [clarification needed] The negative supply V ee is used to forward-bias the emitter junction through R e. The positive supply V cc is used to reverse-bias the collector junction.