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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 ...
A silicon p–n junction in reverse bias. Connecting the p-type region to the negative terminal of the voltage supply and the n-type region to the positive terminal corresponds to reverse bias. If a diode is reverse-biased, the voltage at the cathode is comparatively higher than at the anode. Therefore, very little current flows until the diode ...
If the reverse voltage is increased, then at critical breakdown level, called the reverse breakdown voltage (V BR), an avalanche occurs at J1 and J3 and the reverse current increases rapidly. SCRs are available with reverse blocking capability, which adds to the forward voltage drop because of the need to have a long, low-doped P1 region.
In this mode, electrons are injected from the forward biased n-type emitter region into the p-type base where they diffuse as minority carriers to the reverse-biased n-type collector and are swept away by the electric field in the reverse-biased collector–base junction. For an illustration of forward and reverse bias, see semiconductor diodes.
Layer diagram of thyristor. The thyristor has three p-n junctions (serially named J 1, J 2, J 3 from the anode). When the anode is at a positive potential V AK with respect to the cathode with no voltage applied at the gate, junctions J 1 and J 3 are forward biased, while junction J 2 is reverse biased. As J 2 is reverse biased, no conduction ...
Energy band diagram of a simple NPN w:bipolar junction transistor in forward-active mode showing electron energy versus position. The w:depletion regions of the emitter-base and base-collector junctions are marked.
The additional PN junction blocks reverse current flow. This means that unlike a MOSFET, IGBTs cannot conduct in the reverse direction. In bridge circuits, where reverse current flow is needed, an additional diode (called a freewheeling diode) is placed in anti-parallel with the IGBT to conduct current in the opposite direction. The penalty isn ...
A PIN diode RF microwave switch. Under zero- or reverse-bias (the "off" state), a PIN diode has a low capacitance. The low capacitance will not pass much of an RF signal. Under a forward bias of 1 mA (the "on" state), a typical PIN diode will have an RF resistance of about 1 ohm, making it a good conductor of RF. Consequently, the PIN diode ...