The world of LED Circuit Clinic 5


LED

I think, without an LED, the circuit will be incomplete. It is used as visual indicator in most of the circuits to confirm the working of a particular section. It is a simple diode with light emitting property and hence the name Light Emitting Diode. Its encapsulation has two electrode posts with a chip. When the chip is energized, it emits photons in the form of visible light. The colour of the light depends on the material in the chip. LED works in very low voltage as low as 1 volt. But the new generation White and Blue LEDs require minimum 3 volts to get sufficient brightness. Introduction of the white LED, created a White revolution in the field of LED lighting. Due to its low current consumption, modern lighting system is gradually changing to LED lighting. In addition to White LED, various other types like, Pink LED, Bicolour LED, Multi colour LED etc are also in use . Infrared LED emits light in the Infrared region and hence invisible to eye.
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Zener and Voltage regulation Circuit Clinic 4


CLINIC-3

Zener is not an obsolete device as some designers think. Even though voltage regulator ICs are used widely for precision voltage regulation, Zener diodes are still in use to drop voltage at some sections of the circuit board. Zener is a simple semiconductor device and looks like the glass rectifier diode 1N4148. It generates a fixed voltage output depending on its value. It is designed to operate in the reverse breakdown region. It is always connected in the reverse biased mode with the cathode to the positive supply. Zener diode requires a series resistor to limit current across it, without which the device will be damaged. Zener diodes are available in various voltage ratings from 1.1 volt to 68 volt. Power Zener diodes are also available for industrial applications. They can handle high voltage and current. It’s lead identification is similar to other diodes. The lead near the black or white band is cathode which goes to the positive supply.

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