### Diode

A diode is a PN junction device## Ideal diode**
**

- Conducts with zero resistance when forward biased.
- Offer an infinite resistance when reverse biased.

## Practical Circuit For diode

### The practical characteristic curve for a diode:

Important terms related to diode:

- Knee VoltageKnee voltage is defined as the forward voltage at which the current through the junction starts increasing rapidly.For silicon = 0.7 volt for germanium = 0.3 volt
It is defined as the reciprocal of the slope of the forward characteristic curve.forward resistance**Forward resistance or ac resistance:**

$r_{f}=\frac{1}{\text { slope of forwardcharacteristic }}$

$=\frac{1}{\Delta \mathrm{I}_{\mathrm{f}} / \Delta \mathrm{V}_{\mathrm{f}}}$

$=\frac{\Delta \mathrm{V}_{\mathrm{f}}}{\Delta \mathrm{l}_{\mathrm{f}}}$When the reverse voltage is increased a point is reached when the junction breaks down with sudden rise in reverse current. This value of the voltage is known as the breakdown voltage. Two types of breakdown occur:a.**Junction breakdown :****Zener breakdown:**

a.**Zener breakdown:**

Takes place in junction which are heavily doped so having narrow depletion layers. A very strong electric field appears across the narrow depletion layer which breaks the bond.

b.**Avalanche breakdown :**

Occur in junctions which are lightly doped. (having wide depletion layer) so at a high electric field, the minority charge carriers, while crossing the junction acquire very high velocities. A chain reaction is established, giving rise to the high current.Some electrons and holes have more kinetic energy $\left[\frac{1}{2} \mathrm{mv}^{2}>\mathrm{eV}\right]$ So $\mathrm{e}^{-}$ diffuse from n to p side and hole diffuse from p to n side due to diffusion of the charge carriers a current will flow known as diffusion current.**Diffusion Current :**

a. Because of the concentration difference diffusion occurs.

b. Diffusion results in an electric current from p side to the n side

c. When P-N. Jn is in no Bias = diffusion current = drift current

Net charge flow = 0

Net current = 0**Drift Current:**Due to thermal collisions, the covalent bond is broken. If an electron-hole pair is created in the depletion region, there is a regular flow of electrons towards the n side and of holes towards the p side. Current flow n side to p side called drift current.Drift current and the diffusion current are in the opposite direction

So, that’s it from this blog. I hope you get the idea about what is a diode in electronics. If you found this Explanation helpful then share it with your friends and followers.

Also read

Types of Semiconductor

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