A - Explain the symbols, operating principles and usage areas of the diodes given below. (Zener diode: photo diode: led diode: opto coupler) B- Draw the voltage trigger circuit and explain its operation. Explain how there is a difference between the voltage quadrant and the tripler

Electric Motor Control
10th Edition
ISBN:9781133702818
Author:Herman
Publisher:Herman
Chapter59: Motor Startup And Troubleshooting Basics
Section: Chapter Questions
Problem 12SQ: How is a solid-state diode tested? Explain.
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A - Explain the symbols, operating principles and usage areas of the diodes given below. (Zener diode: photo diode: led diode: opto coupler)

B- Draw the voltage trigger circuit and explain its operation. Explain how there is a difference between the voltage quadrant and the tripler

Expert Solution
Step 1

ZENER diode:-

The ZENER diode is a PN junction diode but this diode operates in the reverse bias mode. This is a special type of PN junction diode which is highly doped. When this diode is highly doped, the concentration of impurity atoms is more in the crystal. This higher concentration of impurity atoms causes a higher concentration of ions in the depletion layer. Therefore, for the applied reverse-biased voltage, the width of the depletion layer becomes smaller than that in a normal diode.

Due to this smaller depletion layer, voltage gradient or electric field strength across the depletion layer is quite large. If the reverse voltage is continued to increase, after a certain applied voltage, the electrons from the covalent bonds within the depletion region come out and make the depletion region conductive. The breakdown occurs is known as the Zener breakdown. The voltage at which this breakdown occurs is called Zener voltage. If the applied reverse voltage across the diode is more than the Zener voltage.

Electrical Engineering homework question answer, step 1, image 1

ZENER diode is generally used in the application of voltage regulators, surge suppressors, etc.

Step 2

Photodiode:-

The photodiode is another type of PN junction diode which consume light energy to produce an electric current. It is also called photo-resistor or photo-sensors.

The working principle involved when a photon of sufficient energy strikes the diode, it generates a couple of an electron-hole pair. This process is also called the inner photoelectric effect. If the absorption begins in the depletion region, then the charge carriers are removed from the junction by the internal electric field of the depletion mode. Hence, the holes in the region start traveling toward the anode, and electrons start traveling toward the cathode, and a photocurrent will be produced. The total current from the diode is the sum of the absence of light and the photo-current.

The symbol of the photo-diode is as shown below,

Electrical Engineering homework question answer, step 2, image 1

The photo-diode is used in the smoke detector, remote control in VCR, compact disc player, etc.

 

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