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The inner workings of an LED, showing circuit (top) and band diagram (bottom) The p–n junction in any direct band gap material emits light when electric current flows through it. This is electroluminescence. Electrons cross from the n-region and recombine with the holes existing in the p-region.
Simple LED (Light Emitting Diode) circuit diagram. In electronics, an LED circuit or LED driver is an electrical circuit used to power a light-emitting diode (LED). The circuit must provide sufficient current to light the LED at the required brightness, but must limit the current to prevent damaging the LED.
Views of a liquid crystal display, both with electroluminescent backlight switched on (top) and switched off (bottom). Electroluminescence (EL) is an optical and electrical phenomenon, in which a material emits light in response to the passage of an electric current or to a strong electric field.
Simple LED circuit with resistor for current limiting. The current in an LED or other diodes rises exponentially with the applied voltage (see Shockley diode equation), so a small change in voltage can cause a large change in current. Current through the LED must be regulated by an external circuit such as a constant current source to prevent ...
Joule thief with regulated output voltage Example of a joule thief circuit driving an LED. The coil consists of a standard ferrite toroid core with two windings of 20 turns each using 0.15 mm (0.006 inch) diameter wire (38 swg) (34-35 AWG). The circuit can utilize an input voltage down to about 0.35 V and can run for weeks using a 1.5 V LR6/AA.
A lemon battery is a simple battery often made for the purpose of education. Typically, a piece of zinc metal (such as a galvanized nail) and a piece of copper (such as a penny) are inserted into a lemon and connected by wires. Power generated by reaction of the metals is used to power a small device such as a light-emitting diode (LED).
Reverse bias: Although the LED is based on a diode junction and is nominally a rectifier, the reverse-breakdown mode for some types can occur at very low voltages and essentially any excess reverse bias can cause immediate degradation, and may lead to vastly accelerated failure. 5 V is a typical maximum reverse bias voltage specification for ...
LED power dissipation is modeled as a current source; thermal resistance is modeled as a resistor; and the ambient temperature is modeled as a voltage source. High power light-emitting diodes (LEDs) can use 350 milliwatts or more in a single LED. Most of the electricity in an LED becomes heat rather than light – about 70% heat and 30% light. [1]