Solving Diode Equation for Current?

In summary, the conversation discusses the difficulty in finding the current due to the presence of I in the exponential term of the equation. The individual is unsure of how to rearrange the equation and asks for pointers. They also inquire about the diode ideality constant and whether there is a way to solve for it. After some discussion and trying different values, it is determined that the constant can be assumed to be 1. The conversation also touches on the use of numerical methods and the potential impact of the diode ideality factor on the current.
  • #1
physics_197
27
0

Homework Statement



I need to find the current, but not sure how to rearrange the equation because of the I in the exp.

Homework Equations



wmbeyd.png


The Attempt at a Solution



Thanks, just need to be pointed in the right direction. Seems like I will either be in ln or exp.
 
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  • #2
Also, just a follow up question, the diode ideality constant... Is there a way to solve for it? My notes just say its between 1 - 1.5, Should I just assume its 1? The manufacturers data sheet does not mention a value for this.
 
  • #3
physics_197 said:

Homework Statement



I need to find the current, but not sure how to rearrange the equation because of the I in the exp.

Homework Equations



wmbeyd.png


The Attempt at a Solution



Thanks, just need to be pointed in the right direction. Seems like I will either be in ln or exp.
Because I appears on its own and as the argment of the exponential, you can't solve for it using elementary operations.
 
  • #4
physics_197 said:
Also, just a follow up question, the diode ideality constant... Is there a way to solve for it? My notes just say its between 1 - 1.5, Should I just assume its 1? The manufacturers data sheet does not mention a value for this.
Are you talking about I0? That one you can solve for.
 
  • #5
No, I'm talking about just I. So how would I go about finding it?
 
  • #6
physics_197 said:
No, I'm talking about just I. So how would I go about finding it?
Using numerical methods
 
  • #7
Thank you, I used Newtons method on matlab, I think it should be correct :)

Also, do any of you have an idea about the diode ideality factor? I am trying to model a PV module in Matlab and the data sheet does not mention this. I read online that people tend to assume its just 1... Any ideas?
 
  • #8
Nevermind! After running through the code using different values (between 1 and 2), There is no difference in terms of the current... well either, it can be neglected or my code is wrong (I tried entering a large number, that affected the current)
 
  • #9
physics_197 said:
Thank you, I used Newtons method on matlab, I think it should be correct :)

Also, do any of you have an idea about the diode ideality factor? I am trying to model a PV module in Matlab and the data sheet does not mention this. I read online that people tend to assume its just 1... Any ideas?
Which variable is the diode ideality factor? That's what I was asking about in post #4.
 

FAQ: Solving Diode Equation for Current?

What is the diode equation for current?

The diode equation for current is I = Is(eV/DVT - 1), where I is the diode current, Is is the reverse saturation current, V is the voltage across the diode, and DVT is the thermal voltage.

How do you solve the diode equation for current?

To solve the diode equation for current, you can use a graphical method or an iterative method. In the graphical method, you plot the diode current versus voltage and find the intersection point with the load line. In the iterative method, you make an initial guess for the voltage and then use the diode equation to calculate the current. If the calculated current is not equal to the desired current, you adjust the voltage and repeat the process until the desired current is achieved.

What is the reverse saturation current in the diode equation?

The reverse saturation current, Is, is the current that flows through a diode when it is reverse biased and there is no voltage across it. It is a characteristic of the diode and is typically very small, ranging from picoamps to nanoamps.

What does the thermal voltage represent in the diode equation?

The thermal voltage, DVT, represents the ratio of thermal energy to electron charge. It is approximately equal to 25 mV at room temperature and is used to account for the temperature dependence of the diode current.

How does the diode equation for current relate to the diode's operating region?

The diode equation for current is used to determine the diode's operating region, which can be forward or reverse biased. When the voltage across the diode is positive, it is in the forward bias region and the current is given by the diode equation. When the voltage across the diode is negative, it is in the reverse bias region and the current is very small, typically on the order of the reverse saturation current.

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