Problems on V - I characteristics

We have studied Ohm’s law in our lower classes.

It 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 us study the V-I characteristics for forward and reverse bias.

The V-I characteristics for the forward bias can be described by the above given graph.

V-I characteristics for reverse bias can be given as shown above.

Let’s solve a problem based on V-I characteristics.

V-I characteristics of a silicon diode are given above.

We have to find resistance at .

To solve this, we will consider a straight line between and

Now, for corresponding voltage is .

And, for corresponding voltage is .

Here, we can use Ohm’s law to find R.


On solving further,

Therefore, forward bias resistance of the given diode is


V-I characteristics are different for different biasing.

It can be described for, 1- Forward bias 2- Reverse bias

For the forward bias, it can be described by a graph as shown above.

And for reverse bias, the graph given above shows V-I characteristics.

The end