# Determine diode current (1 Viewer)

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#### HebrewHammer

1. The problem statement, all variables and given/known data

Determine the diode current with Is=50nA and an applied forward bias of 0.6V

2. Relevant equations

Id = Is ( e ^ (kVd/Tk) - 1)

3. The attempt at a solution

So my teacher is horrible and this is what I have been able to collect on my own.

Is = 50 and Vd = 0.6v
I'm pretty sure k is refering to Boltzmann’s constant k = 1.38 x 10^-23 J.K-1.
I'm pretty sure Tk is the room temperature in kelvin so that would be 298.

Plugging it all in I get
Id = 50 ( e ^ (((1.38 x 10^-23)(.6))/298)-1)

This gives me an answer of 1.389*10^-24
Something seems really off, if one of those constants I figured out is wrong please let me know.

#### Redbelly98

Staff Emeritus
Homework Helper
The exponential term should actually be

e ^ [e·Vd / (k·T)]​

where e is the charge of an electron, k is Boltzmann's constant, and T is absolute temperature. (Vd is the diode voltage, of course.)

Also, you seem to be using 50 Amps for Is, when it is actually 50 nA.

#### HebrewHammer

Ok so I figured out how to do it.

50nA(e^(.6/298)-1) =

50nA(.002015) =

10.077nA

Seems like I was overthinking it. Now theres a part 2 to this question that I am really lost on.

Determine the diode current at 20 degrees C for a silicon diode with Is=0.1uA at a reverse bias potential of -10v.

Further help would be awesome.

#### Redbelly98

Staff Emeritus
Homework Helper
Ok so I figured out how to do it.

50nA(e^(.6/298)-1) =

50nA(.002015) =

10.077nA

Seems like I was overthinking it.
There's still a problem. You have completely left e and k out of your calculation!

Now theres a part 2 to this question that I am really lost on.

Determine the diode current at 20 degrees C for a silicon diode with Is=0.1uA at a reverse bias potential of -10v.

Further help would be awesome.
You are given Vd and the temperature, so just apply the same equation. (Don't forget about e and k.)

#### HebrewHammer

ok i got the answer i think

.1(e^(-10/293)-1) =

= -.00335nA

Seems off to me but its the same procedure.

#### Redbelly98

Staff Emeritus
Homework Helper
There's still a problem. You have completely left e and k out of your calculation!

The exponential term should actually be
e^[e·Vd / (k·T)]​
where e is the charge of an electron, and k is Boltzmann's constant.

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