How do you calculate V_on for a diode?

[TecHNooB]

Need to know this to solve a problem 🙁

Clarification:
Basically, I have to model real diodes behavior as an ideal diode, V_on, and R in series. How do I find V_on?

I'm given a graph of I_d vs V_d with the y-axis on a ln scale (the V-I characteristic looks like a straight line with some positive slope).

 

[PottedMeat]

Uh what kind of diode? An LED? Or a plain old rectifier?

 

[JohnCU]

assume .7 and go

i think it's lower for germanium diodes though like .3 or .4

 

[TecHNooB]

Originally posted by: JohnCU
assume .7 and go

Can't for this problem.

It's a plain ass diode.

 

[JohnCU]

Originally posted by: TecHNooB

Originally posted by: JohnCU
assume .7 and go

Can't for this problem.

It's a plain ass diode.

what do you have? just a circuit? details?

 

[PottedMeat]

what info did they give you? doping levels?

 

[krotchy]

so are you talking like the V vs I curve on it or something? Like at 1mA it will have a forward bias of say .65V and at 1A it might be .75 or something assuming that was your diodes character. In that case take the minimum forward bias current voltage and make that the Von, then find the maximum forward bias current voltage, and subtract Von. Now you have Vdelta (Vmax-Von). Divide by Vdelta by Imax and you are set.

Or do I not get what the crap your teacher wants here?