What is an LED Diode?
A LED is a semiconductor device that uses electroluminescence. It has a p-n junction just like any other diode and when electrons recombine with holes they produce light.
An LED requires a current-limiting resistor for proper operation. This prevents the LED from overheating and destroying itself.
What is a LED?
All diodes release light when they are powered but LEDs are specially designed to release a large number of photons in a focused direction. They are essentially solid-state lamps and bulbs that can be made very small, highly efficient and long-lived. LEDs are also very rugged and can be re-cycled many times without suffering damage or failure.
The LED is based on gallium arsenide semiconductor material which has a larger band gap than silicon based diodes. This allows electrons to pass across the semiconductor more easily and gives off energy as a photon in the visible range of the spectrum. By varying the precise composition of the semiconductor compound the wavelength or colour of the emitted light can be changed.
Another feature of the LED is that it generates very little heat and can be operated at a lower voltage than most other lamps and bulbs. This can make them more compact and help with the design of more portable dc to ac inverter products. In addition, the LEDs are very fast to turn on and can reach full brightness in a microsecond.
Like a normal diode, an LED has a positive and negative side called the Anode and Cathode. The Anode is marked by having a longer lead and is connected to the voltage supply while the Cathode is marked by a shorter lead and is the negative side of the device.
LED Construction
Essentially, an LED is just a normal diode that’s been designed specifically to emit light. They operate the same as a standard general purpose pn junction diode but are built with compound semiconductor materials that emit light when current flows through them.
The different elements in the compound semiconductor material (like gallium, arsenic and phosphorus) are mixed in varying proportions to produce different wavelengths of light when an electric current is passed through them. This is what gives LEDs their color, and it is the reason they can produce such a wide range of colors.
To make an LED emit light, it must be forward biased which means its cathode terminal is connected to the negative side of the power supply or battery and its anode terminal is connected to the positive side. In this case, the n layer has a majority of electrons and the p layer has a majority of holes. When current is flowed through an LED, the electrons and holes recombine at the PN junction to create light.
Because of the small amount of current required to make an LED emit light, they are very efficient devices with low power dissipation. This allows them to be used in applications where space is limited and they can easily be wired in parallel or series with other LEDs to form displays like bargraphs, strips, arrays and seven segment displays.
LED Intensity
The light output intensity of an LED is directly related to the current passing through it. Unlike a resistor where the resistance stays constant, LEDs have a dynamic resistance that changes with the applied voltage and current. This is why LED data sheets usually show a forward current to voltage curve.
This characteristic makes the LED a perfect choice for indicators where they are switched on and off often. In fact, a typical indicator LED can reach full brightness in under a microsecond. LEDs can also be used for display lighting and billboard or sign lights that are cycled frequently.
Another advantage of LEDs is that they can be dimmed by lowering the current passing through them. This can be achieved by using a pulse-width modulation (PWM) circuit with a short duty cycle or by simply adding a variable resistance component like a rheostat.
It is also worth noting that the reverse polarity voltage of an rtc electronic component LED is not fixed and can vary between different devices and even between individual LEDs of the same type. This means that a protection resistor in series with the LED is needed to avoid damaging it permanently.
LED Color
Unlike traditional bulbs that use a tungsten filament that gives off light as it gets heated, LEDs emit light through the phenomenon of electroluminescence. This is caused by the recombination of electrons and holes in the semiconductor material. An LED has a p-n junction which means that when current flows through it, it passes through the negative and positive ends of the material (called anode and cathode). The electrons pass through the anode and are trapped by the cathode, which then emits photons. LEDs emit a specific color based on the type of semiconductor material used and the amount of doping.
A single-color LED produces a narrow band of wavelengths in the visible spectrum. Its brightness depends on the wavelength emitted and the eye’s sensitivity at that wavelength. LEDs can also emit in the near infrared and ultraviolet regions through careful composition of the semiconductor material.
LEDs can be made to produce more than one color by using multiple diode dies in the same case. This is called a bi-color LED. A simple example is red and green LEDs that are combined to produce a yellow or amber light. A more advanced application is a single package that contains three different LED colors: red, green, and blue. When the appropriate current is applied to each diode, a wide range of shades can be produced.