Spark
Loading...

Diodes and LEDs (PN Junction Basics)

← Builds on Breadboard and Multimeter Skills (Hands-on Practice)

Terms you will need

  • electronAn electron is a tiny particle that carries a negative electric charge and moves around the nucleus of an atom.

How this topic runs

  1. 1Start here
  2. 2How it works
  3. 3At competition depth

Diodes and LEDs are fundamental components in modern electronics, playing a crucial role in controlling the flow of electric current. A diode is a two-terminal electronic component that allows current to flow in one direction while blocking it in the opposite direction. This unidirectional behavior is due to the properties of a PN junction, which is formed by joining p-type and n-type semiconductor materials. LEDs, or light-emitting diodes, are a special type of diode that emit light when an electric current passes through them. They are widely used in various applications, from indicator lights in electronic devices to high-efficiency lighting solutions. Understanding the basic principles of diodes and LEDs is essential for anyone interested in electronics, as they form the foundation for more complex circuits and technologies.

Figures (4)

Figure A. A p–n junction in thermal equilibrium with zero bias voltage applied. Electron and hole concentration are reported with blue and red lines, respectively. Gray regions are charge-neutral. Light-red zone is positively charged. Light-blue zone is negatively charged. The electric field is shown on the bottom, the electrostatic force on electrons and holes and the direction in which the diffusion tends to move electrons and holes. (The log concentration curves should actually be smoother with slope varying with field strength.)
A p–n junction diode in low forward bias mode. The depletion width decreases as voltage increases. Both p and n junctions are doped at a 1e15/cm3 doping level, leading to built-in potential of ~0.59V. Observe the different quasi Fermi levels for conduction band and valence band in n and p regions (red curves).
Silicon atoms (Si) enlarged about 45,000,000x (Image size approximately 955 pm × 955 pm)
Figure B. A p–n junction in thermal equilibrium with zero bias voltage applied. Under the junction, plots for the charge density, the electric field, and the voltage are reported. (The log concentration curves should actually be smoother, like the voltage.)

Diodes are electronic components that let electricity flow in one direction but block it in the other. This happens because of a special structure called a PN junction. A PN junction is made by joining two types of semiconductor materials: p-type and n-type.

In p-type, there are more positive charges, and in n-type, there are more negative charges. When these two are joined, they create a one-way path for current. This happens because the energy from the current causes the material in the LED to release light.

To picture this, imagine a gate that only opens in one direction. When you push in the right way, it opens and lets current through, and in the case of an LED, it also makes light. This gate-like behavior is what makes diodes and LEDs essential in many electronic devices.

Key Points

    Terms

    Tap a term for a plain-language explanation.

    Sources & licensing(4)