Learn Electronic Circuits - Diodes

 

What is diode?

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A diode is a semiconductor device that primarily allows the flow of electric current in one direction while blocking it in the opposite direction. It serves as a one-way valve for electrical current and is a fundamental building block in electronic circuits. Diodes have a wide range of applications in electronics, from signal rectification and protection to voltage regulation and switching.

Here are some key characteristics and functions of diodes:

1.     One-Way Current Flow: The primary function of a diode is to enforce one-way current flow in a circuit. When a voltage is applied across the diode terminals in the forward bias direction (anode to cathode), it allows current to flow with minimal resistance, behaving like a closed switch. In the reverse bias direction (cathode to anode), the diode blocks the flow of current, acting as an open switch.

2.     Rectification: Diodes are commonly used for signal rectification, converting alternating current (AC) into direct current (DC). In a half-wave rectifier, a diode allows only the positive half of an AC waveform to pass, resulting in a pulsating DC output. In a full-wave rectifier, two diodes are used to convert both halves of the AC waveform into DC.

3.     Protection: Diodes are often employed for overvoltage protection. Zener diodes, a specific type of diode, can regulate voltage and protect sensitive components by maintaining a constant output voltage across their terminals, even when the input voltage exceeds a certain threshold.

4.     Voltage Clamping: Diodes can be used to clamp voltage levels in circuits. A common application is the use of diodes in clamp or clipper circuits to limit the amplitude of signals within a specific range.

5.     Switching: Diodes can be used as switches in high-frequency applications, such as in digital logic gates and signal switching circuits. Fast-recovery diodes and Schottky diodes are commonly used for their rapid switching characteristics.

6.     Signal Protection: Diodes protect sensitive components, such as transistors, from reverse voltage or voltage spikes that can damage them. Diodes in parallel with a relay coil, for example, can provide a path for the reverse EMF generated when the coil is de-energized.

Common types of diodes include:

·         Rectifier Diodes: Used for rectification and converting AC to DC.

·         Zener Diodes: Used for voltage regulation and voltage reference.

·         Light-Emitting Diodes (LEDs): Emit light when current flows through them and are used for displays, indicators, and lighting.

·         Schottky Diodes: Known for their fast switching speeds and low forward voltage drop, often used in high-frequency applications.

·         Varactor Diodes (Varicap Diodes): Used for voltage-controlled capacitance in tuning circuits.

·         Photodiodes: Convert light into electrical current, commonly used in light sensors and optical communication.

·         Avalanche Diodes: Operate in the reverse breakdown region and can be used as voltage references and in noise generation.

Diodes play a crucial role in modern electronics, enabling various functions and protections within electronic circuits. Their simplicity and reliability make them essential components in countless electronic devices and applications.