Forward Bias Characteristics For the V-I characteristics of a forward biasing P-N junction diode the experimental circuit arrangement is shown in the
figure.
Here the applied voltage V on the diode is changed by the potential divider arrangement which can be easily read by the voltmeter connected in parallel to the diode. The current I flowing in the diode related to various values of voltages are noted by a milliammeter.
In this way, the curve obtained for different values of V and I is shown in the figure. which is also called as the P-N junction diode forward bias characteristic curve.
In forward biasing for every less value of voltage. (for Ge is 0.3 V and for Si is 0.7 V) the forward current is very less. The reason for this is that the value of applied voltage is less than the potential barrier due to which the flow of the current is not uniform. This behavior of the diode is represented by the OA part of the curve. When the value of applied potential is more increased the current in the diode increases exponentially.
This behaviour is shown by part AB. The potential at which the current’s value increase very rapidly is called the diode’s knee voltage or cut in voltage. For germanium diode its value is approximately 0.3 V and for silicon diode its value is 0.7V.
