A PN junction diode is formed when a p-type semi- conducter is fused to an N type semi- conducter creating  a potential barrier voltage across the  diode junction  which as aresult of the diffusion of holes and electrons form their respective zones.

A PN junction is one of the simplest semi conductor devices available. It conducts current in one direction only.It is a non ohmic conductor which has the characteristic of I-V giving a non linear gragh, when Ohms law equation is applied.

The N zone is obtained when an intrinsic semi conductor is doped with a pentavalent impurity atoms, the region acts as donors with electron as the majority charge carriers .The P zone holes at the majority charge carriers obtained when the acceptor impurity is added.

The diffusion of holes and electrons creates a  depletion layer between the two zones due to the uncovered fixed ions. A  junction diode is connected in the circuit to overcome or enhance  the potential barrier by connecting it to the external voltage (forward biasing and reverse biasing).

How should the diode be connected in a circuit so that its forward biased and reverse biased?

• Sketch on your exercise books the possible circuits.