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}=ΔIΔV $
On solving further,
$ΔV=0.8−0.7=0.1V$
$ΔI=20−10=10mA=10_{−2}A$
$∴R_{fb}=10_{2}0.1 $
$=0.1×10_{−2}Ω$
$∴R_{fb}=10Ω$
Therefore, forward bias resistance of the given diode is
$10Ω.$
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