V - I Characteristics of P-N Junction Diode

We must have gone through Ohm’s law during our lower classes.

Ohm’s law states that potential difference ‘V’ is directly proportional to the current ‘I’ .

Similarly, for a semiconductor diode, we apply a voltage across it and study its current.

This is shown by the V-I graph known as V-I characteristics.

V-I characteristics are different for different biasing.

Let’s learn about V-I characteristics in forward bias.

The silicon diode given above is forward biased.

The graph given shows the V-I characteristic of a diode in forward bias

In the forward bias initially current increases very slowly for increasing voltage.

But after certain voltage, current increases significantly.

This voltage is called as Threshold voltage or cut-in-voltage.

The threshold voltage is represented by $V_{th}.$ For Silicon, $V_{th}\sim 0.7V$ For germanium, $V_{th}\sim 0.2V$

Now let’s learn in reverse bias

The given silicon diode is reverse biased.

V-I characteristics in reverse bias can be seen in the graph above,

In reverse bias, The current almost remains constant with a change in bias.

This constant current is known as reverse saturation current.

But after certain maximum voltage, current rises rapidly.

This maximum voltage is called as the Breakdown voltage.

Revision

V-I characteristics are different for different biasing.

The V-I characteristics are different for the forward bias and reverse bias

For the forward bias, it can be described by a given graph.

The graph given below shows V-I characteristics in reverse bias,

The End