Theory:

PN diode is formed by joining p-type semiconductor with n type semiconductor. It is done by various techniques. The diode works only when some potential is applied to it.

Forward Biasing:

When p-type is connected to positive terminal and n-type is connected to negative terminal of battery. Diode is said to be forward biased as a result width of potential barrier is reduced there and small forward voltage is needed to overcome the barrier potential. Barrier is eliminated current starts flowing.

Reverse Biasing:

When p-type is connected to negative terminal and N-type is connected positive terminal of the battery diode is said to be reverse biased. As a result the width of potential barrier in diode is increased and it prevents across the junction. Thus, a high resistance path is established for circuit and hence current is continued to increase then electrons get enough kinetic energy.

Forward Biased Characteristics:

1. Assemble the circuits as shown in the figure. The switch just side of the voltmeter is kept towards the F.B. side and the other switch below the ammeter is termed as towards the 10mA side.
2. Now increase the voltage (V_f) and note the current (I_f).
3. A graph is plotted between V_f and I_f. It will be similar to the one shown in the figure.

Reverse Biased Characteristics:

1. Assemble the circuit as shown in the figure. The switch just side of the voltmeter is kept towards the R.B. side and the other switch below the ammeter is towards the µa side.
2. Now, the voltage V_R is increased gradually and the corresponding current I_R is noted.
3. A graph is plotted between V_R and I_R. It will be similar to the one shown in the figure.