Why is Reverse Saturation Current Included in the Forward Bias Diode Equation?

[Muhammad Usman]

TL;DR

why reverse current or dark saturation current is considered if the diode is forward biased ?

Hi all,

This is not homework help or something, it is my general query. I read that ideal diode equation is given as

in above equation Is is the reverse saturation current or dark saturation current (According to this website). And according to most of the study which I did this reverse saturation current doesn't exist while the diode is forward biased, I want to ask that why this parameter is still in equation if it does not exist in first place, thanksUsman

 

[phyzguy]

You are misunderstanding. This parameter I_s is the multiplier that determines the amount of current that flows when forward biased. It is very important in forward bias. Of course, this equation is for an ideal diode. For a real diode, there are other things that contribute to the reverse biased current. So in a real diode, one typically determines I_s by measurements in the forward biased region, not in reverse bias.

 

[Baluncore]

I_s can also be seen as a "scale current", that is dependent on the area of the diode. That is why it can be used for both modes of operation.