Applications Of Diode

Step 1: What is LED? LED means Light Emitting Diode. It is a p-n junction diode that emits light when current passes through it.

Step 2: Condition for current flow. A diode conducts significant current in forward bias. In reverse bias, only negligible leakage current flows and no useful light is emitted.

Step 3: What happens in forward bias? When forward biased:
• Electrons from n-side move toward junction.
• Holes from p-side move toward junction.
• Recombination occurs near junction.
• Energy is released as photons (light).

Step 4: Why not reverse bias? Reverse bias increases depletion region and prevents recombination current, so LED does not normally emit light.

Step 5: Conclusion. Hence LED is operated for emission in forward bias only. $ $

Concept: Physics (Semiconductors) - Transistor Parameters and .

Step 1: Recall the standard relationships. In a transistor, is the current gain in a common base configuration and is the current gain in a common emitter configuration. They are related by: $ \frac{1}{\alpha} = \frac{1}{\beta} + 1 \implies \frac{1}{\alpha} = \frac{1 + \beta}{\beta} \implies \alpha = \frac{\beta}{1 + \beta} \alpha = \frac{\beta}{1 + \beta} \frac{1}{\beta} = \frac{1}{\alpha} - 1 \implies \frac{1}{\beta} = \frac{1 - \alpha}{\alpha} \implies \beta = \frac{\alpha}{1 - \alpha} \alpha = \frac{\beta}{1 - \beta} \alpha = \frac{\beta}{1 + \beta} $

Since, an LED is forward biased diode, so its characteristics are those of forward bias, i.e., Here, option (a) is characteristics of a diode in forward and reverse bias. Option (c) characteristics of solar cell. Option (d) reverse bias characteristics 1 drawn in first quadrant can be photodiode or Zener diode.