summary of P–N Junction Diodes

summary

A junction diode is created by joining N-type and P-type materials together.

● The region near the junction is referred to as the depletion region. Electrons cross the junction from the N-type to the P-type material, and thus both

the holes and the electrons near the junction are depleted.

The size of the depletion region is limited by the charge on each side of the junction.

● The charge at the junction creates a voltage called the barrier voltage.

● The barrier voltage is 0.3 V for germanium and

0.7 V for silicon.

● A current flows through a diode only when the external voltage is greater than the barrier voltage.

● A diode that is forward biased conducts currenta. The P-type material is connected to the positive terminal, and the N-type material is connected to the negative terminal.

● A diode that is reverse biased conducts only a small leakage current.

● A diode is a one-directional device.

● The manufacturer specifies a diode’s maximum forward current and reverse voltages.

The schematic symbol for a diode is

introduction to basic electricity and electronics technology-0320

● In a diode, the cathode is the N-type material, and the anode is the P-type material.

● Diodes can be constructed by the grown junction, alloyed junction, or diffused junction method.

● The diffused junction method is the one most often used.

● Packages for diodes of less than 3 A identify the cathode end of the diode with a black, white, or silver band.

● A diode is tested by comparing the forward to the reverse resistance with an ohmmeter.

● When a diode is forward biased, the resistance is low.

● When a diode is reverse biased, the resistance is high.

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