Jonction pn diode pdf

If one side of a single crystal of pure semiconductor Ge or Si is doped with acceptor impurity atoms and the other side is doped with donor impurity atoms, a PN junction is formed as shown in Fig P region has a high concentration of holes and N region contains a large number of electrons.

As soon as the junction is formed, free electrons and holes cross through the junction by the process of diffusion. During this process, the electrons crossing the junction from N-region into the P region, recombine with holes in the P-region very close to the junction. Similarly holes crossing the junction from the P-region into the.

N-region, recombine with electrons in the N-region very close to the junction. Thus a region is formed, which does not have any mobile charges very close to the junction. This region is called depletion region. In this region, on the left side of the junction, the acceptor atoms become negative ions and on the right side of the junction, the donor atoms become positive ions Fig 9.

An electric field is set up, between the donor and acceptor ions in the depletion region. The potential at the N-side is higher than the potential at P-side. Therefore electrons in the N-side are prevented to go to the lower potential of P-side. Similarly, holes in the P-side find themselves at a lower potential and are prevented to cross to the N-side.

Thus, there is a barrier at the junction which opposes the movement of the majority charge carriers. Hence it is a device with two elements, the P-Type forms anode and has an excess of holes whereas, the N-Type forms the cathode and has an excess of electrons.

These terminals are brought out to make the external connections. This means that there are no available charge carries in this region. This charge transfer of electrons and holes across the PN junction is known as diffusion. In view of the fact that this area is depleted of charge carriers it is known as the depletion region.

The semiconductor diode PN junction with no bias applied Diode as a Conductor: When a voltage is applied current will flow. The Depletion Region shrinks allowing current to flow. Therefore, a diode acts like a conductor since it allows current to pass in one direction.

This is Forward Bias. The semiconductor diode PN junction with forward bias Diode as an Insulator: When the battery polarity is reversed, the Holes move away from the Depletion Region as does the Free Electrons expanding the Depletion Region thus restricting the movement of current.

It acts as an insulator since it blocks current passing in the opposite direction. This is Reverse Biasing. VD is the voltage across the diode. The DC power supply was switched on and the value of VS source voltage was set to 0. The corresponding values of ID current through the diode and VD voltage across the diode were measured.

Subsequently, they were noted in the table. After that the value of VS was changed to 0. The values of VS were changed in an interval of 0. This straight line is called as Load line and it is drawn on the i-v characteristics curve of the Diode. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel.

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