Trying to find info about LEDs you’ll use in your circuits? Find it all here in this LED characteristics tutorial.
Introduction
LEDs are the main components used for signal lighting in electronics. If you want to know if your module is powered on, you’ll usually use an LED. LEDs can also be used as a heartbeat or signaling element, telling you that your circuit is alive and producing output. However, each LED characteristic can be different in many ways. Here, you’ll find the essential characteristics of LEDs.
LED Characteristics
LED Color vs. Forward Voltage
Color is one of the most important characteristics of an LED. However, it’s not just about color; the forward voltage drop of an LED is also affected by this property. Different radiated colors come from different semiconductor materials, each having its own forward voltage characteristic. See the table below.
| LED Color Type | Semiconductor Material | Forward Voltage | Efficiency |
|---|---|---|---|
| Standard Green LED | Gallium Phosphide (GaP) or Aluminum Gallium Indium Phosphide (AlGaInP) | 2.1V - 3.0V | Moderate |
| High-Brightness Green LED | Indium Gallium Nitride (InGaN) | 3.0V - 4.0V | High |
| Standard Red LED | Gallium Arsenide Phosphide (GaAsP) or Gallium Phosphide (GaP) | 1.6V - 2.2V | Moderate |
| High-Brightness Red LED | Aluminum Gallium Indium Phosphide (AlGaInP) or Gallium Aluminum Arsenide Phosphide (GaAlAsP) | 1.8V - 2.5V | High |
| Standard Yellow LED | Gallium Arsenide Phosphide (GaAsP) or Gallium Phosphide (GaP) | 2.0V - 2.3V | Moderate |
| High-Brightness Yellow LED | Aluminum Gallium Indium Phosphide (AlGaInP) | 2.1V - 2.5V | High |
| Standard Blue LED | Zinc Selenide (ZnSe) or Silicon Carbide (SiC) | 2.5V - 3.2V | Moderate |
| High-Brightness Blue LED | Indium Gallium Nitride (InGaN) | 3.0V - 4.0V | High |
| Standard Orange LED | Gallium Arsenide Phosphide (GaAsP) or Gallium Phosphide (GaP) | 2.0V - 2.2V | Moderate |
| High-Brightness Orange LED | Aluminum Gallium Indium Phosphide (AlGaInP) | 2.1V - 2.5V | High |
In addition to this, each LED color can have standard or high brightness. High brightness usually uses more modern technology as it is more efficient than standard. If your LED is unusually dim despite applying the recommended current, it’s probably old stock.
LED Forward Current
LEDs are current-driven semiconductor devices. With this, the current value is critical in determining your preferred brightness. A series resistor is used to define the current, however, the forward voltage drop also plays a major role in this. The usual maximum LED current is 20mA for optimal brightness. Below is an example computation:
LED current = (Supply Voltage – LED voltage) / Series Resistor
If you have a supply voltage of 5V, a green LED voltage of 3V, and plan to use an LED current of just about 10mA :
Series Resistor = (Supply Voltage – LED voltage) / LED current
Series Resistor = (5V – 3V) / 10mA
Series Resistor = 200 ohms
Series Resistor Power Rating
After determining your LED forward current and series resistance, you should now determine if your series resistor can handle the power. Different resistors have different maximum power dissipation that they can handle. It’s critical that you are far away from this value, or else you can damage your circuit.
Below is an example of computing the maximum power dissipation of a resistor in series with an LED:
From the computation above:
P_Resistor = I^2 * R
P_Resistor = (10mA)^2 * 200
P_Resistor = 20mW
or
P_Resistor = V^2 / R
P_Resistor = (5V – 3V)^2 / 200
P_Resistor = 20mW
You may use any resistor that’s for away from this value. If you’re using SMD, you can use a 0603 type (max 100mW). For a through-hole component, you may use 1/8W (125mW) or 1/4W (250mW).
Conclusion
This article presented essential LED characteristics. These characteristics include LED color, forward voltage, forward current, series resistor value, and maximum power dissipation. Hope you have learned a lot in this tutorial :).
