Diode Equation and Saturation Current

  • Thread starter DeldotB
  • Start date
  • #1
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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.
 

Answers and Replies

  • #2
berkeman
Mentor
61,370
11,892
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
154
0
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.
 

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