The document discusses the basics of a PN junction and diode. A PN junction forms at the interface between P-type and N-type semiconductor materials. This junction acts as a diode that allows current to flow easily in one direction, but restricts it in the reverse direction. Forward bias occurs when the positive terminal is connected to the P region and negative to the N region, allowing current flow. Reverse bias widens the depletion region until the potential stops majority carrier current, while a very small minority carrier current still flows.

1. Lecture 3
P-n Junction and Diode

2. 2
Basic Diode Concepts
The PN-Junction
* The interface in-between p-type and n-type material is called a
pn-junction.
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4. There is no movement of
charge through a pn-
junction at equilibrium.
* The pn-junction form a
diode which allows
current in only one
direction and prevent
the current in the other
direction as determined
by the bias.
Diodes – Basic Diode Concepts

5. 5
*Forward Bias: dc voltage positive terminal connected to the p region and
negative to the n region. It is the condition that permits current
through the pn-junction of a diode.

6. 6
*Forward Bias: dc voltage positive terminal connected to the p region and
negative to the n region. It is the condition that permits current
through the pn-junction of a diode.

7. 7
*Forward Bias:

8. 8
*Reverse Bias: dc voltage negative terminal connected to the p region
and positive to the n region. Depletion region widens until its
potential difference equals the bias voltage, majority-carrier current
ceases.

9. 9
10. Diodes – Basic Diode Concepts
*Reverse Bias:
majority-carrier current ceases.
* However, there is still a very
small current produced by
minority carriers.

10. 10
* Reverse Breakdown: As reverse voltage reach certain value,
avalanche occurs and generates large current.

11. 11
The Diode Characteristic I-V Curve