Why Is A Resistor Used With An Led

Lets do one more example this time with a white led you can find some here and a 3xaa battery box such as this one. An led usually has a resistor connected in series with it because an led light emitting diode is not linear in current to voltage like a resistor and has to be operated within specified.

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Apply a bit more voltage and there is current and the led lights up.

Why is a resistor used with an led. In parallel circuits the total circuit current is divided among all of the branch. The ballast resistor is used to limit the current through the led and to prevent that it burns. Proper parallel led circuits have a series resistor for each led.

Reply 2 years ago reply upvote. Obviously that does not work with leds because they dont behave like a linear resistor. Such a resistor is often called a ballast resistor.

The simplest circuit to power an led is a voltage source with a resistor and an led in series. An led light emitting diode emits light when an electric current passes through it. There are some cases where you can drive leds in series without a resistor like in our led dining table circuit but in most cases its preferable and safer to use a resistor.

Leds are semiconductors diodes in particular. Why do you need a resistor with an led. It mitigates most of the unpredictable properties of leds.

If you look at the graph above you can rise the voltage from 0 volt to 16 volt without resulting in noticeable current. To limit the current in the led to a safe value. The resistance of the ballast resistor is easy to calculate with ohms law and kirchhoffs circuit laws.

This is why we use an series resistor with leds when current is not constant. If the voltage source is equal to the voltage drop of the led no resistor is required. The current flowing in an led is an exponential function of voltage across the led.

I am an engineering student and have performed various practicals related to logic gates in which led is my output devicei always have used 330w470w resistor in series with the ledbut i dont know the reason behind thati even know that without that resistor led sometimes malfunctions causing it to stop working. The ballast resistor is used to limit the current through the led and to prevent that it burns.

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