Diodes - Definition, Symbol, Types, Applications, FAQs

Diode definition: Diode meaning is a semiconductor which works as a single-way switch. It permits current to flow freely in one direction while restricting current flow in the other.
The original diode was a two-electron tube of evacuated glass or metal, a negative cathode and a positive anode. In electronic diode circuits like radio and television receivers, they were utilised as rectifiers and detectors. When the anode (or plate) is exposed to a positive voltage, electrons released from the heated cathode travel to the plate and then back to the cathode through an external power supply. Electrons cannot leave from the cathode when a negative voltage is supplied to the plate, hence no plate current flows. Electrons can flow from the cathode to the plate, but not from the plate to the cathode, in a diode. Anode (positive lead) and cathode (negative lead) establish the polarity of a diode (negative lead). Most diodes allow current to flow when the anode is given a positive voltage.

What is Diode?

A diode has two diode terminals and is an electrical component with only a single direction (so long as it is operated within a specified voltage level). The ideal diode has zero resistance in one direction, but in the other it has endless resistance.

A p-n junction is the most common type of diode. One material (n) with electrons as charge carriers abuts a second material (p) with holes (places depleted of electrons that behave as positively charged particles) as charge carriers in this type of diode. A depletion area forms at their interface, via which electrons diffuse to fill holes in the p-side.

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Diode Symbol

Symbolic diode image or diode diagram

Above is an example of a conventional diode unit sign. Two diode terminals, known as anode and cathode, may be seen in the diagram above. The anode in the forward biased situation is the arrowhead, which symbolises the direction of conventional current flow. The cathode is located on the other end of the diode circuit.

Construction of Diode

Electrical diode can be made from silicon or germanium, two semiconductor materials. When the anode voltage exceeds the cathode voltage and the diode conducts readily with minimum voltage loss, the diode is said to be forward-biased. When the cathode voltage exceeds the anode voltage, the diode is regarded to be reverse-biased. The arrow in the symbol represents the conventional current flow direction when a diode conducts.

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Semiconductor Diode and Types of Diode

Normal (p–n) diode are commonly built of doped silicon or germanium and operate as explained above. Cuprous oxide and later selenium were employed before the discovery of silicon power rectifier diode. Because of their low efficiency, a much higher forward voltage and a large heat sink (often extending the metal substratum of the diode) were required, both of which were much higher than the later silicón diode of a similar current rating.

Light Emitting Diode (LED):

Light is produced by passing an electric current between the electrodes through a light emitting diode (LED). In other words, when a sufficient quantity of advancing current runs through it, light is produced. This light is not visible in many diode because the frequency levels are too low to allow viewing. Different colours of LEDs are available. Tricolour LEDs are LEDs that can emit three colours at once. The energy gap of the semiconductor employed determines the colour of light.

1. Laser Diode:

A laser diode produces coherent light, making it a unique sort of diode. It's found in a lot of CD players, DVD players, and laser printers. These are more expensive than LEDs but less expensive than other laser producers. The only disadvantage of these diode is their short life.

2. Avalanche Diode:
   This is a reverse bias diode that uses the avalanche effect to operate. The avalanche breaks down when the voltage drop is consistent and independent of current. They are utilised for photo detection because of their high sensitivity.
3. Zener diode:

The most useful sort of diode is the Zener diode, which can offer a stable reference voltage. These are reverse biassed and break down when a particular voltage is applied. A stable voltage is established when the current travelling through the resistor is limited. In power supply, zener diodes are commonly employed to give a reference voltage.

4. Schottky Diode:

Compared to other silicon PN junction diode, it has a lower forward voltage. Where there is low current and voltage varies between 0.15 and 0.4 volts, the decrease will be seen. In order to achieve that performance, these are built differently. In rectifier applications, Schottky diodes are widely employed.

5. Photodiode:

A photodiode can detect even the tiniest quantity of current flow caused by light. These are quite useful in detecting light. This is a reverse bias diode, which is commonly seen in solar cells and photometers. They're even used as power generators.

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6. P-N Junction Diode:

Rectifier diodes are also known as P-N junction diodes. These diodes are composed of semiconductor material and are utilised in the rectification process. Two layers of semiconductors make up a P-N junction diode. P-type material is doped in one layer of the semiconductor material, while N-type material is doped in the other. The P-N junction is formed by the combination of these both P and N-type layers. As a result, the diode is known as a P-N junction diode.

The P-N junction diode permits current to flow in one direction but prevents it from flowing in the opposite direction.

Applications of Diode

The following are some of the diode's applications and uses:

1. A rectifier made of diode.

2. In the clipping diode circuit, there are two diode.

3. Clamping diode circuits with diode.

4. Logical gates with diode.

5. Reverse current protection diode.

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