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 $I=15mA$.

To solve this, we will consider a straight line between $10mA$ and $20mA.$

Now, for $I=20mA$ corresponding voltage is $0.8V$.

And, for $I=10mA$ corresponding voltage is $0.7V$.

Here, we can use Ohm’s law to find R.

Therefore, $R_{fb}=\frac{\Delta V}{\Delta I}$

On solving further, $\Delta V=0.8-0.7=0.1V$ $\Delta I=20-10=10mA=10^{-2}A$

$\therefore R_{fb}=\frac{0.1}{10^2}$ $=0.1\times 10^{-2}\Omega$

$\therefore R_{fb}=10\Omega$

Therefore, forward bias resistance of the given diode is $10\Omega .$

Revision

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