Operating Principles of Diodes & LEDs
LEDs are found nearly everywhere, ranging in implementation from traffic signals to digital computers and residential lighting. Known for their diverse color range and impeccable longevity, LEDs are the first lighting choice for many engineers and building planners. With this lighting technology, the fundamental working component is the diode, which is a semiconductor that manipulates a circuit to perform intended actions. In this article, we will discuss everything you need to know about diodes and how they work to emit light in the case of LEDs.
The name diode comes from this device's two-electrode terminal, which conducts current in a single direction. The purest example of this is the diode's forward and reverse-biased functions. In a forward-biased state, the diode allows current to travel freely between its two terminals, with the impetus being a properly placed battery. If the battery is placed backward in the circuit, the diode switches to a reverse-biased state, disallowing any current from flowing through its terminals. In this manner, the diode acts as a switch at the most basic level.
In order for a diode to function properly in a circuit, it must be optimally placed. This may be intuitive because the diode deals with directional flow, and a reversal in installation could not yield the intended results. Particularly, diodes contain a positive anode terminal and a negative cathode terminal. In this design, current can only flow from the anode to the cathode, with the reverse being impossible. Luckily, most diodes are clearly labeled with an arrow or “+” and “-” on either end, allowing quick and proper installation.
Diodes are preferentially made of silicon or germanium, which are very popular among all semiconductors due to their stability. However, both elements are poor conductors because they prefer covalent bonding and act as insulators instead. In order for these elements to be converted to semiconductors, engineers add a particular amount of impurities in a process called doping to increase their conductive capacity. Electrons can either be added or removed in doping, making the end product positive or negative. The positively doped elements are called p-type, while negatively charged semiconductors gain the title of n-type. The n-to-p connection of diodes allows them to have their regulatory properties.
In order for a diode to be activated, it must receive a minimum current called the forward voltage (VF), with this number varying between the semiconductor materials. For example, silicon-based diodes generally require a VF of .6-1v, while germanium-based diodes only require .3v.
In an LED, light is produced as a particular current passes through the diode. The voltage of their current determines the color of the light produced, allowing for a wide variety of visuals. Compared to incandescent bulbs, LEDs produce markedly less heat and are therefore much more efficient. They also cost less in every domain compared to other lighting techniques, and due to their long lifespan, they continue to be a great investment. LEDs are also easy to implement and control wirelessly, making them extremely popular as residential and commercial lighting fixtures. Finally, LEDs can be easily dimmed by modulating the voltage entering the diode.
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