Piecewise Linear Diode Model

In summary, the conversation is about a specific section and question in a past paper for a course. The question involves using equations to find the resistance of a circuit and includes a diagram. The user also mentions difficulties with using Paint to draw the diagram and provides a link to the question.
  • #1
eximius
29
0
Note: This is a past paper, I'm simply revising for an exam. But I thought that this was the best forum to stick it in.

Homework Statement



http://exampapers.cf.ac.uk/papers/engin/en1051/en1051a09.pdf

Section A, Q1 c

[PLAIN]http://img684.imageshack.us/img684/9695/questionm.jpg

Homework Equations



R1 = V1/I1
Rp = (V2-V1)/(I2-I1) = R1||R2
R2 = RpR1/(Rp-R1)

The Attempt at a Solution



R1 = 0.5/280x10-6 = 1785.71 ohms
Rp = (0.54 - 0.5) / (680x10-6 - 250x10-6) = 0.04 / 4x10-4 = 100ohms = R1||R2
R2 = RpR1/(Rp-R1) = 178571 / (-1685.71) = -105.9322185 = -105.93 ohms
V1 = 0.5V

Diagram -

[PLAIN]http://img407.imageshack.us/img407/4486/diagrame.jpg

Forgive the wrong symbols, difficult with paint.
 
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  • #2
That link:

A username and password are being requested by https://exampapers.cf.ac.uk . The site says: "Enter your Cardiff University username & password"

Can you post the question rather than link to it please.
 
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  • #3
Zryn said:
That link:



Can you post the question rather than link to it please.

Sorry I've fixed it.
 
  • #4
Bump, sorry.
 
  • #5
I understand the method of solving the problem, but I am not sure what the question is asking. Can anyone clarify?

The Piecewise Linear Diode Model is a simplified model used to describe the behavior of a diode in a circuit. It divides the diode's operation into two regions: forward and reverse bias. In the forward bias region, the diode behaves like a short circuit and allows current to flow. In the reverse bias region, the diode behaves like an open circuit and does not allow current to flow.

To solve this problem, you first need to find the resistance of the diode in the forward bias region (R1). This can be calculated using Ohm's law, where R1 = V1/I1. Next, you need to find the equivalent resistance of the diode in the reverse bias region (Rp). This can be calculated using the formula Rp = (V2-V1)/(I2-I1) = R1||R2, where R2 is the resistance of the diode in the reverse bias region. Finally, you can use the formula R2 = RpR1/(Rp-R1) to calculate the value of R2.

In this problem, the question is asking you to calculate the value of R2. However, it is important to note that the calculated value of R2 is a negative value (-105.93 ohms). This is because the diode is in the reverse bias region, where it behaves like an open circuit, and therefore has an infinite resistance. The negative value is simply a mathematical representation of this behavior.
 

1. What is a Piecewise Linear Diode Model?

A Piecewise Linear Diode Model is a mathematical representation of a diode's behavior that takes into account its non-linear characteristics. It is used to simulate the diode's voltage-current relationship in electronic circuits.

2. How does a Piecewise Linear Diode Model work?

The model divides the diode's voltage-current curve into multiple linear segments, each representing a different operating region of the diode. The segments are connected at specific points, or "knees," to create a piecewise linear approximation of the non-linear curve.

3. What are the advantages of using a Piecewise Linear Diode Model?

Using a Piecewise Linear Diode Model allows for more accurate simulation of the diode's behavior in electronic circuits. It also simplifies the analysis and design of circuits containing multiple diodes.

4. Are there any limitations to the Piecewise Linear Diode Model?

Yes, the model is an approximation and may not accurately represent the behavior of a diode in all operating conditions. It also does not take into account some factors such as temperature and parasitic effects.

5. How is a Piecewise Linear Diode Model different from other diode models?

Unlike other models such as the Shockley diode equation, the Piecewise Linear Diode Model does not require complex mathematical calculations and can be easily implemented in circuit simulation software. It also provides a closer representation of the diode's behavior compared to simpler models.

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