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The Shockley equation doesn't model this, but adding a resistance in series will. The reverse breakdown region (particularly of interest for Zener diodes) is not modeled by the Shockley equation. The Shockley equation doesn't model noise (such as Johnson–Nyquist noise from the internal resistance, or shot noise).
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 Shockley ideal diode equation or the diode law (named after the bipolar junction transistor co-inventor William Bradford Shockley) models the exponential current–voltage (I–V) relationship of diodes in moderate forward or reverse bias. The article Shockley diode equation provides details.
It is a PNPN diode with alternating layers of P-type and N-type material. It is equivalent to a thyristor with a disconnected gate. Shockley diodes were manufactured and marketed by Shockley Semiconductor Laboratory in the late 1950s. The Shockley diode has a negative resistance characteristic. [1] It was largely superseded by the diac.
Output resistance is found using a small-signal model for the circuit, shown in Figure 2. Transistor Q 1 is replaced by its small-signal emitter resistance r E because it is diode connected. [10] Transistor Q 2 is replaced with its hybrid-pi model. A test current I x is attached at the output.
By the Shockley diode equation, the current diverted through the diode is: = { []} [7] where I 0, reverse saturation current; n, diode ideality factor (1 for an ideal diode) q, elementary charge; k, Boltzmann constant
The former component can be described with the formula , whereas represents the sheet resistance of the semiconductor substrate and the width of the metal pads. The other component that contributes to the total resistance is denoted by 2 R C {\displaystyle 2R_{C}} because when two adjacent pads are characterized two identical metallized areas ...
The voltage versus current characteristics of an LED is similar to any diode. Current is approximately an exponential function of voltage according to the Shockley diode equation, and a small voltage change may result in a large change in current. If the voltage is below or equal to the threshold no current flows and the result is an unlit LED.