Diode numerical (calculation of current and voltage across diode)

In summary, the diode in the circuit shown below has the nonlinear terminal characteristics as shown in the figure.The formula ηVT / Id is the slope of a Si diode's exponential V-I characteristic, and gives the Silicon diode's small signal resistance.
  • #1
lazyaditya
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The Diode in the circuit shown below has the non linear terminal characteristics as shown in the figure.Let the voltage be "coswt" V . Question 3.1.33 and my attempt is shown in the figure.
 

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  • #2
The formula ηVT / Id is the slope of a Si diode's exponential V-I characteristic, and gives the Silicon diode's small signal resistance. You don't have a Si diode for this question, you have some clunky diode whose V-I graph has a fixed slope regardless of Id.

I would much prefer that you typed out the text of a question, rather than forcing me to jockey back and forth between multiple graphics (and wasting my 3G data quota unnecessarily in the process).
 
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  • #3
Sorry for inconvenience.
 
  • #4
Can i calculate the voltage at output using superposition theorem . Considering dc voltage and ac voltage sources separately.
 
  • #5
lazyaditya said:
Can i calculate the voltage at output using superposition theorem . Considering dc voltage and ac voltage sources separately.
Yes, that should work out.

Did you get the right answer for 3.1.33?
 
  • #6
No i didn't , i get very confused with this concept. When using superposition theorem and considering DC signal first i took cut off voltage and forward resistance of diode into consideration to get output voltage 1,when i considered AC signal then also should i take cut off voltage of diode into consideration ?
 
  • #7
But i did understood that i shouldn't use dynamic resistance of diode in this case .
 
  • #8
lazyaditya said:
No i didn't , i get very confused with this concept. When using superposition theorem and considering DC signal first i took cut off voltage and forward resistance of diode into consideration to get output voltage 1,when i considered AC signal then also should i take cut off voltage of diode into consideration ?
AC is synonymous with "small-signal" and also "incremental", it imposes what amounts to just a tiny wobble in the DC. So this small wobble does not see the 0.6 V cut-off, it sees just how the current increases for a tiny increase in voltage: the dynamic resistance or incremental resistance, and this is the slope of the diode's graph at the DC bias point.

Of course, you should from the outset confirm that the AC component really is small compared with the DC. There may be occasions when an examiner deliberately sets a trick question to catch anyone not fully awake.
 
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  • #9
Since you're given multiple choice, you can proceed as follows:
Let Vin = 2 + 1 = 3V (highest input voltage)
Sum currents to zero at the anode
write expression for diode current assuming v > 0.5V. This should be obvious from the diagram.
Solve for diode current, then diode voltage.
 
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  • #10
Thank you for help. Problem solved :)
 

FAQ: Diode numerical (calculation of current and voltage across diode)

1. What is a diode?

A diode is a two-terminal electronic component that allows current to flow in only one direction. It is made up of a semiconductor material, such as silicon, and has a p-n junction that acts as a one-way valve for electric current.

2. How do I calculate the current and voltage across a diode?

To calculate the current and voltage across a diode, you can use the diode equation, which is I = IS(e^(V/VT) - 1), where I is the current, IS is the saturation current, V is the voltage, and VT is the thermal voltage. You will also need to know the diode's characteristics, such as its forward voltage drop and maximum current rating.

3. What factors affect the current and voltage across a diode?

The current and voltage across a diode can be affected by several factors, including the diode's characteristics, such as its forward voltage drop and maximum current rating, as well as the temperature, ambient conditions, and the circuit in which the diode is used. It is important to consider these factors when calculating the current and voltage across a diode.

4. Can I use the same calculation for all types of diodes?

No, the calculation of current and voltage across a diode may vary depending on the type of diode. Different types of diodes, such as Zener diodes or Schottky diodes, have different characteristics and require different equations to calculate their current and voltage. It is important to use the correct equation for the specific type of diode being used.

5. How can I ensure the accuracy of my diode current and voltage calculations?

To ensure the accuracy of your diode current and voltage calculations, it is important to use the correct equations for the specific type of diode being used. Additionally, double-checking your calculations and taking into account any external factors that may affect the diode's performance can help ensure the accuracy of your results.

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