We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is an LED Circuit?

By G. Robinson
Updated Feb 02, 2024
Our promise to you
WiseGeek is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGeek, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

An LED circuit is any electrical power circuit used to power light-emitting diodes, or LEDs. At its simplest, an LED circuit comprises a voltage source, a resistor to reduce the voltage, and an LED. The LED circuit may contain other components too, such as switches and sensors, but these don't affect the basic principles involved in powering an LED.

LEDs are cheap, reliable, robust, and energy efficient. The LED circuit has become a common feature in electronic devices, automobiles, and appliances, where they serve as indicator lights and for minor illumination. Larger LEDs have been developed that have home applications, and these will no doubt become more important in the future, but this discussion will concentrate on the elements of a the LED circuit as it applies to smaller LEDs.

LEDs are simple, solid-state diodes. A diode is a device that allows electrons to flow in only one direction by interposing a bit of semiconductor material in the current's path at what's known as the junction. In LEDs, this semiconducting material is specially treated to emit photons of light when current passes through it. When electrical current passes through the LED in the right direction, it's said to be forward biased and the semiconductor material in the junction glows.

When the flow of current is reversed, a condition known as reverse bias, no electrons flow through the semiconducting material and no light is emitted. Excess reverse bias voltage will easily damage the junction, so this reverse breakdown voltage must be guarded against. For this reason, direct current is preferred to alternating current for powering LEDs, making batteries ideal power sources.

Excess forward bias voltage may also damage the LED junction, so a resistor is almost always used to reduce the voltage to the device. LEDs are rated by the manufacturer regarding both their current draw and their resistive voltage drop under forward bias, or Vf, and these must be taken into consideration when choosing a resistor for an LED circuit. The value of the necessary resistor can be calculated by subtracting the LED's resistive voltage drop from the power supply voltage, and dividing the results by the LED's listed current rating.

The danger of reverse breakdown voltage makes it critical that the LED be placed in the LED circuit with the correct polarity. LEDs allow electrons to pass from their cathodes to their anodes, so LEDs must be wired so that their cathodes connect to the negative pole of the power supply and their anodes to the positive side. Manufacturers indicate the polarity of the LED in several ways, notably by making the cathode wire shorter, flat, black, or by flattening or notching the cathode side of the LED case.

The typical LED circuit as used to power a small indicator light will use a 1.5 to 9 V battery as a power source. It will have a typical forward voltage drop, about 1.8 to 3.3 volts, depending on the color. The LED will draw perhaps 5 to 20 mA of current.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.