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The Shockley diode equation, or the diode law, named after transistor co-inventor William Shockley of Bell Labs, models the exponential current–voltage (I–V) relationship of semiconductor diodes in moderate constant current forward bias or reverse bias:
The Shockley diode equation relates the diode current of a p-n junction diode to the diode voltage .This relationship is the diode I-V characteristic: = (), where is the saturation current or scale current of the diode (the magnitude of the current that flows for negative in excess of a few , typically 10 −12 A).
The narrowing of the collector does not have a significant effect as the collector is much longer than the base. The emitter–base junction is unchanged because the emitter–base voltage is the same. Base-narrowing has two consequences that affect the current: There is a lesser chance for recombination within the "smaller" base region.
In a circuit with a three terminal device, such as a transistor, the current–voltage curve of the collector-emitter current depends on the base current. This is depicted on graphs by a series of (I C –V CE) curves at different base currents. A load line drawn on this graph shows how the base current will affect the operating point of the ...
The collector–emitter current can be viewed as being controlled by the base–emitter current (current control), or by the base–emitter voltage (voltage control). These views are related by the current–voltage relation of the base–emitter junction, which is the usual exponential current–voltage curve of a p–n junction (diode).
Thus, as long as the Zener current (I Z) is above a certain level (called holding current), the voltage across the Zener diode (V Z) will be constant. Resistor, R1, supplies the Zener current and the base current (I B) of NPN transistor (Q1). The constant Zener voltage is applied across the base of Q1 and emitter resistor, R2.
(This is opposite to the direction of current in a forward-biased diode, such as a light-emitting diode in operation.) When the pair is created outside the space charge zone, where the electric field is smaller, diffusion also acts to move the carriers, but the junction still plays a role by sweeping any electrons that reach it from the p side ...
Diode I-V diagram. Breakdown voltage is a parameter of a diode that defines the largest reverse voltage that can be applied without causing an exponential increase in the leakage current in the diode. Exceeding the breakdown voltage of a diode, per se, is not destructive; although, exceeding its current capacity will be.
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