Dear Franklin,

The diode i-v characteristics can be plotted on a linear scale. Then one draw the best fitted straight line in the conduction region.

The interception of the straight line with the voltage axes determines the the called cut in or the threshold voltage of the diode. The inverse of the slope of the straight line is called the forward on resistance of the diode rF.

The equation fitting the diode characteristics can be expressed by:

VF= Vgamma + IF rF,

or

IF= (VF-Vgamma)/ rF,

You can use Excel to make the graphical plots and the best linear fitting of the measured curve.

You can your self develop an algorithm for the best fitting.

It is so that the mean square error must be minimum,

Hence,

SUM ( Im- IF)^2 over all points must be minimum.

You can start with an estimated values of Vgamma and rF at two points in the high current range. That is you choose two points at the higher current range to satisfy the linear equation.

Best wishes

U can see one example in the following paper... Article Chemically Doped Random Network Carbon Nanotube p-n Junction...

Dear Franklin,

Not at all.

The cut in voltage = the threshold voltage, It is the not the cut off voltage. It is the voltage at which appreciable conduction starts.

The onset of the conduction or the cut in voltage is an approximate boundary between the conduction off region and the conduction on region of the diode. It is obtained by the best straight line fitting.

I would like that you read this part of the book given in the following link:Book Electronic Devices

After reading the book the subject will be very clear to you.

Best wishes

Dear Abdelhalim:

Thank you for your time, and for this nice resource, and congratulations for this book and for the work in Semiconductor devices it seems you guys are doing over there,

now, after I read the book I will try the fittings on my curves to try to have a better interpretation of the sections of the IV curves.

Best Regards !

Dear Abdelhalim:

I looked up at the Chapter 3 of your book, specially from Static J-V Characteristic of a PN junction Diode 'till the end. But i could n't find the criteria or the methodology to define the conduction region of the on junction diode response in the I-V curve.

The upper limit is somewhat clear, since i can look on the graph 'till I reach the breakdown voltage, but it is being difficult for me to stablish a methodic criteria to chose the lower limit (on my positive bias region).

Please give a look at one of my graphs , I hope you can give me an advice of what could be the best way to chose these two limits in my curves, to get a reliable value of the cut in voltage and have an standardized procedure:

I appreciate the help,

Thank you sir !

Dear Abdelhalim:

I'm sorry, were you able to give a look at my graph ?

I appreciate it ! :)

Thank you, Regards !