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Electronics Tutorial

Diode

P N junction diode

A diode is a fundamental electronic component that allows current to flow in one direction while blocking it in the opposite direction. It is a two-terminal device typically made from a semiconductor material such as silicon or germanium. The diode’s behaviour is based on the interaction between the P-N junction, which is formed by joining a p-type semiconductor (excess of holes) with an n-type semiconductor (excess of electrons).

Forward Bias

Diode forward bias

When a diode is forward-biased, meaning the positive terminal of a power source is connected to the P-side and the negative terminal to the N-side. The negative terminal repulse the electrons from the N-side and the positive terminal repulse the holes from the P-side. So, the depletion region shrinks as the voltage reaches the threshold voltage thus the diode allows current to flow freely. The threshold voltage depends on the type of semiconductor is being used in the diode. For instance Silicon has a threshold voltage of 0.7V.

Reverse Bias

Diode reverse bias

On the other hand, when a diode is reverse-biased, with the positive terminal connected to the N-side and the negative terminal to the P-side. The positive terminal attracts the electrons of the N-side toward itself and the negative terminal attracts the holes of P-side. So the depletion region gets wider and block the current flow.

Diodes have several practical applications. They are commonly used in rectifier circuits to convert alternating current (AC) into direct current (DC). They can also be employed in voltage clamping and voltage regulation circuits, as well as in signal modulation and demodulation circuits. Light-emitting diodes (LEDs) are a specialised type of diode that emit light when forward-biased, and they are widely used in displays, indicators, and lighting applications.

In summary, a diode is an electronic component that allows current to flow in one direction while blocking it in the opposite direction. It plays a crucial role in various electronic circuits and has applications ranging from rectification to signal processing and lighting.

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