Pn Junction As Rectifier Pdf Free

PN Junction as Rectifier

A PN junction is a device that allows current to flow in one direction but not in the other. It is formed by joining two types of semiconductor materials, one with excess electrons (N-type) and one with excess holes (P-type). A PN junction has many applications in electronics, such as solar cells, light-emitting diodes, and diode lasers. One of the most common uses of a PN junction is as a rectifier, which converts alternating current (AC) to direct current (DC).

How does a PN junction work?

When a PN junction is first formed, there is a concentration gradient of charge carriers across the interface. Electrons from the N-type region diffuse into the P-type region, and holes from the P-type region diffuse into the N-type region. This creates a region near the junction where there are no free carriers, called the depletion region. The depletion region has a net positive charge on the N-side and a net negative charge on the P-side, creating an electric field that opposes further diffusion of carriers. The electric field also creates a potential difference across the junction, called the built-in potential.

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When an external voltage is applied to the PN junction, it can either increase or decrease the potential difference across the junction, depending on the polarity of the voltage. If the external voltage is positive on the P-side and negative on the N-side, it is called forward bias. In this case, the external voltage reduces the potential barrier for the carriers to cross the junction, and a large current flows through the device. If the external voltage is negative on the P-side and positive on the N-side, it is called reverse bias. In this case, the external voltage increases the potential barrier for the carriers to cross the junction, and a very small current flows through the device.

How does a PN junction act as a rectifier?

A rectifier is a device that converts AC to DC. AC is a type of electric current that changes its direction periodically, while DC is a type of electric current that flows in one direction only. A rectifier can be made by connecting a PN junction in series with a load resistor, as shown in Figure 1.

Figure 1: A rectifier circuit with a PN junction and a load resistor

When the input voltage is positive on the P-side and negative on the N-side, the PN junction is forward biased and allows current to flow through the circuit. When the input voltage is negative on the P-side and positive on the N-side, the PN junction is reverse biased and blocks current from flowing through the circuit. Therefore, only half of the input voltage cycle passes through the circuit, creating a pulsating DC output voltage.

Where can I find more information about PN junctions and rectifiers?

If you are interested in learning more about PN junctions and rectifiers, you can find some useful resources online. Here are some links to free PDF files that explain these topics in more detail:

• [PN and MetalSemiconductor Junctions - Chenming Hu]

• [Lecture 9: PN Junctions - University of California, Berkeley]

• [SEMICONDUCTORS AND P-N JUNCTIONS - University of Cincinnati]