Diode Equation and Saturation Current

In summary, the diode equation can be written as I(V)=I_{sat}e^{\frac{Ve}{nKT}}-I_{sat}, with the second term being negligible if V> > nV_{T}. Vt is the thermal voltage and n is a factor related to the quality of the material. With initial conditions V> 0.1V, kT\approx .025 eV, and n\approx 2, it can be shown that V is much greater than n*thermal voltage. The reason for the saturation current being negligible is due to the majority of the current flowing in the forward direction and the reverse current, caused by minority carriers, being low. This is typically in the order
  • #1
DeldotB
117
7
Good day all:

For the diode equation: [tex]I(V)=I_{sat}e^{\frac{Ve}{nKT}}-I_{sat}[/tex]

I also know that the second term in the equation is negligible if: [tex]V> > nV_{T}[/tex]

Vt is thermal voltage
n is ...just a factor related to the quality of the material

I have these initial conditions:
[tex]V> 0.1V\, \, \, ,kT\approx .025 eV\, \, \, n\approx 2[/tex]

Its easy to show that the my inital conditions lead to a V much greater that n*thermal voltage.

My question is: Why is the saturation Current negligible? I know it has something to do with recombination rate but can anyone give me a simple explanation? So many websites just say that the order relation is true but give no evidence as to why.
 
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  • #2
In forward bias, the Is component is tiny. You only see it in reverse bias before avalanche breakdown...

http://www.electrotechservices.com/electronics/images/diode_graph.jpg
diode_graph.jpg

Does that help?
 
  • #3
Because most of the current is in the forward direction and the reverse current, due to the minority carriers, is low. Typically in the order of nA to uA.
 

Related to Diode Equation and Saturation Current

1. What is the diode equation?

The diode equation is a mathematical expression that describes the relationship between the voltage across a diode and the current flowing through it. It is typically written as I = I0(eV/DVT - 1), where I is the diode current, I0 is the saturation current, V is the voltage across the diode, and DVT is the thermal voltage.

2. What is the saturation current?

The saturation current, also known as the reverse saturation current or leakage current, is the current that flows through a diode when it is reverse biased and no other external factors are affecting it. It is a characteristic of the diode and is typically very small, on the order of nanoamps or picoamps.

3. How does temperature affect the diode equation and saturation current?

As temperature increases, the diode equation and saturation current can both be affected. The thermal voltage DVT in the diode equation is directly proportional to temperature, so as temperature increases, the diode current will also increase. Additionally, the saturation current is typically affected by temperature, with higher temperatures resulting in a higher saturation current.

4. What is the significance of the diode equation and saturation current in practical applications?

The diode equation and saturation current are important in understanding the behavior of diodes in various circuits and applications. They can help predict the voltage and current characteristics of a diode, and are crucial in designing and analyzing diode-based circuits such as rectifiers, voltage regulators, and switching circuits.

5. Can the diode equation and saturation current be used to model all types of diodes?

The diode equation and saturation current are based on the ideal diode model, which assumes an ideal diode with no resistance or capacitance. While this model may be sufficient for some diodes, it may not accurately represent the behavior of all types of diodes, such as Zener diodes or LEDs. Therefore, the diode equation and saturation current may need to be modified or additional equations may need to be used to accurately model these types of diodes.

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