What are Semiconductor Diodes? Explain ideal diode? Application and CHARACTERISTICS

 Semiconductor Diodes

A semiconductor diode is a two-terminal electronic device that conducts current primarily in one direction. It is made of semiconductor material, usually silicon, and acts as a switch or rectifier, converting AC to DC.

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Diodes are one of the oldest and most widely used electronic devices. Diodes can be defined as nearly unidirectional conductors whose state of conductivity is determined by the polarity of the terminal voltage. A semiconductor diode is formed by the metallurgical junction of p-type and n-type materials. (P-type materials are group-IV elements doped with small amounts of V-group material; an n-type material is a group-IV base element doped with a group-III material.)

Semiconductor Diode Examples

Examples of semiconductor diodes include:

• LED (Light Emitting Diode)
• Zener diode
• Schottky diode
• Photodiode
• PIN diode
• Tunnel diode
• Varactor diode
• Gunn diode
• IMPATT diode.                              

THE IDEAL DIODE

The device has two terminals with an anode (p-type) and cathode (n-type). This makes it easier to choose the diode as the name. When the terminal voltage is non-negative (VD ≥ 0), the diode is said to be forward-biased, and the ð Positive current through ( iD ≥ 0 ) is called forward current. If VD< 0, the diode is said to be reverse bias and the corresponding small negative current is called the reverse current.

An ideal diode is a complete two-state device that exhibits zero impedance when biased forward. The impedance at the time of reverse bias is infinite because either the current or the voltage is zero at any instant, and the diode does not consume power. Forward diode voltage for many circuit applications Drop and reverse current are small compared to other circuit variables. Then accurate results are obtained if the actual diode is modeled as ideal.

Application of Semiconductor Diodes

Applications of semiconductor diodes include:

• Power rectification in power supplies and chargers
• Clipping and limiting in audio and radio circuits
• Detection and mixing in radio communication systems
• Switching in digital circuits
• Light detection and emission in optical communication systems
• Voltage regulation in Zener diode circuits
• Laser light generation in laser diodes
• Solar cell operation as photodiodes
• Voltage control in varactor diodes
• Microwave generation in Gunn diodes.

DIODE TERMINAL CHARACTERISTICS

Using the Fermi-Dirac probability function to predict charge neutralization gives a static (unchanged with time) equation for the diode junction current:

                            ID = I0 (evD/ηVT - 1) Ampere 

Where VT  kT=q; V 

vD = diode terminal voltage, V 

I0  = temperature-dependent saturation current, A 

T = absolute temperature of the p-n junction, K 

k = Boltzmann’s constant (1.38 × 10-23 J/K) 

q electron charge (1.6× 10-19 C) 

η =empirical constant, 1 for Ge and 2 for Si 

 

Types of Diodes

• P-N Junction Diode, Rectifier Diode, Schottky Diode, Light Emitting Diode (LED), PhotodiodeLaser Diode, Zener Diode, Gold Doped Diode, Constant Current Diode, Vacuum Diode, PINDiode, Shockley Diode, Point Contact Diode.

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