Semiconductor Fundamentals: Diodes and LED Technology

Semiconductors

Semiconductors have revolutionized the world of electronics. With the appearance of integrated circuits, technology has taken a significant step into the future. Their primary advantages include reduced size, low power consumption, and affordability.

Semiconductor Diodes

A semiconductor diode is a component that allows current to flow in one direction only. Its application is particularly useful in circuits where this unidirectional quality is essential.

The Junction Diode

A junction diode is formed by joining a P-type crystal with an N-type crystal. When connected to a battery such that the positive pole coincides with the P-type crystal and the negative pole with the N-type, negative charges are repelled toward the junction, allowing current to flow.

Forward-Biased Diode Characteristics

Forward bias determines the relationship between bias voltage and current. Significant current flow does not begin until a minimum potential difference is applied.

Reverse-Biased Diode Characteristics

In reverse bias, the N-type crystal is connected to the positive terminal of the battery, and the P-type crystal is connected to the negative terminal, effectively blocking current flow.

Power and Rated Current

Diodes are designed to operate optimally under specific nominal conditions. Risks include:

• Exceeding the reverse breakdown voltage.
• Exceeding the maximum rated power.

Diodes have a specific capacity to dissipate heat produced at the junction. If the power produced exceeds this dissipation capacity, the component may fail.

LED: Light Emitting Diode

LEDs are used to display numbers and letters in various devices. They are manufactured by joining two PN semiconductor crystals. When biased with a direct voltage, valence electrons from the N-type crystal traverse the junction and recombine with holes in the P-type crystal, emitting light.

Characteristics of LEDs

• Direct-tension: The voltage drop that occurs across the LED when direct current flows.
• Direct excitation current: The current required to reach the desired light intensity.
• Reverse current: The current that may flow through the diode when reverse-biased.
• Power dissipation: The portion of power that is not converted into light and degrades into heat, which must be evacuated.