Definition of Diode

The diode is an electronic component consisting of two poles and functions to rectify the current. This component consists of combining two semiconductors each of which are given different doping (material addition), and additional conductor material for power supply.

Diode Components

The main structure of the diode is two poles of conductor electrodes each connected to a p-type silicon-type and silicon semiconductor. Anode is an electrode connected to a p-type silicon in which fewer electrons are involved, and a cathode is an electrode connected with a n-type silicon in which more electrons are contained. The meeting between silicon n and silicon p will form a border called PN Junction.
Semiconductor materials used are generally silicon or germanium. The p-type semiconductor was created by adding a material having a valence electron of less than 4 (Example: Boron) and a n-type semiconductor was created by adding a material having more than 4 valence electrodes (Example: Phosphorus).

How Diodes Work

Simply put, the workings of diodes can be described in three conditions, ie conditions without voltage, given forward biased, and negative (reverse biased) voltage.

Conditions without voltage

At no given voltage conditions will form an electric field border on the PN junction region. This happens begins with the diffusion process, ie moving the charge electro from side n to the p side. The electrons will occupy a place on the p side called the holes. The movement of electrons will leave positive ions on the n side, and holes filled with electrons will generate negative ions on the p side. These immobile ions will form a static electric field which blocks the movement of electrons in the diode.


Positive voltage conditions (Forward-biased)
In this condition, the anode portion is connected to the positive terminal of the power source and the cathode port is connected to the negative terminal. The existence of an external voltage will result in the ions that become electric barrier becomes attracted to each pole. The negative ions will be attracted to the positive anode side, and positive ions will be attracted to the negative cathode side. The loss of the barriers will enable the movement of electrons inside the diode, so that the electric current can flow as in a closed circuit.

Negative voltage conditions (Reverse-biased)

In this condition, the anode portion is connected to the negative terminal of the power source and the cathode port is connected to the positive terminal. The existence of an external voltage will result in the ions that become electric barrier becomes attracted to each pole. Negative voltage delivery will make negative ions attracted to the cathode side (n-type) given a positive voltage, and positive ions are attracted to the anode side (p-type) given a negative voltage. The movement of the ions is in the direction of a static electric field that blocks the movement of electrons, so that the barrier will be thicker by the ions. As a result, electricity can not flow through the diode and the circuit is likened to an open circuit.

Types of Diodes and Functions of Diodes

Diodes are divided into several types based on their characteristics and functions.The types of diodes and their applications are as follows.

• PN Junction Diode: A standard diode consisting of a PN arrangement and having a working manner as described earlier. This type of diode is a commonly used diode on the market (also called generic diode), used mainly as a current rectifier.
•  Light Emitting Diode (LED): When fed by forward-bias currents, the LED will emit light. LEDs are currently commonly used as illumination devices and some types are used to replace fluorescent lamps.
• Laser Diode: The laser type diode also produces light, but the resulting light is coherent light. The laser diode application is a CD and DVD reading device and laser pointer.
• Photodiode: Photodiode can generate electrical energy when PN junction area irradiated. Generally the photodiode is operated in reverse-bias, so a small current due to light can be directly detected. Photodiode is used to detect light (photodetector).
• Gunn Diode: Gunn Diode is a type of diode that does not have a PN Junction, but consists only of two electrodes. This type of diode can be used to generate microwave signals.
• BARITT Diode: BARITT (Barrier Injection Transit Time) Diode is a type of diode that works with thermionic emission principle. This diode is used to produce microwave signal with low noise level.
• Tunnel Diode: Tunnel Diode is a diode that works utilizing one of the quantum mechanical phenomena of tunneling. The tunnel junction is used as one of the components in the oscillator, amplifier, or signal mixer, especially since its velocity reacts to changes in voltage.
• Backward Diode: The backward diode has a similar characteristic to the tunnel, the difference lies in the presence of the doped lower side than the opposite side. This difference in doping profile makes the backward diode has similar voltage-current characteristics at reverse and forward conditions.
• Diode PIN: In the PIN diode, there is an intrinsic semiconductor area (without doping) placed between P and N junction. The effect of adding these intrinsic areas is the widening of depletion areas that limit the movement of electrons, and this is best used for switching applications.
• Schottky Diode: At Schottky diode an additional metal is added to the center of the semiconductor surface. Characteristics of the advantages of this diode are low activation voltage and short recovery time. These diodes are very common for high-frequency electronic circuits, such as radio devices and logic gates.
• Step Recovery Diode: The semiconductor part of this diode has a doping level that gradually decreases with the lowest point in the junction. This modification can reduce switching time because the load in the junction area is less. The appli- cation of this semiconductor is in radio frequency electronic devices.
• Varactor Diode: Applied to a regular reverse mode with an adjustable barrier layer given the applied voltage. This makes this diode as if it is a capacitor.
• Zener diode: It has a special characteristic that lets the breakdown effect during reverse bias This diode can produce a fixed voltage and is commonly used as a reference voltage generator in electronic circuits.

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