# Reverse/forward voltage explained?

Hey,

i am looking to buy some LED's for an upcoming project but I have been confused by the terms reverse voltage and forward voltage.

Which one reffers to the voltage required if the LEd is corrected in the right way.

for example, buying some LED's from ebay it saisd this
"Forward Voltage typ/max: 2.2V/2.8V
Reverse Voltage: 5V "

Does that mean with the LED connected (anode positive and cathode negative) i would need 5volts of power? or would i need 2.2/2.8volts?

thanks

Good answer, one thing to remember with any LED of any Type or Colour, is the brightness and longevity varies with the forward Voltage. In the example given 2.2 Volts would light it at decent functional brightness and last literally for Years, but running it at anywhere above 2.8 V will make it very bright but not for nearly as long.

steveastrouk3 years ago
The FORWARD voltage is the volt drop through the LED, when the nominal current is flowing, when the ANODE is more positve than the CATHODE. Here, you will see betwen 2.2 and 2.8V in normal operation.

REVERSE voltage is the maximum the LED can stand the other way round without damage.
7 months ago

as someone who found this on a google search, this answer is flipping awesome and clear, thankyou!

7 months ago

recordmasta001 (author)  steveastrouk3 years ago
So how do i determine what voltage power supply to use for the LEDS?
3 years ago
As steveastrouk points out,
The Power supply needs to be greater then the forward voltage plus
an extra minimum of two more volts.   Six or nine volts are favorite values.
You must plan to put a resistor in series with the LED.
Pay attention, not to exceed the recommended LED current,
or the longevity will be cut down fast !
3 years ago
Take the FORWARD voltage, as the critical parameter and the rated forward current.

The rest depends on how many you want to deploy, and what voltage you have available to drive them.

Steve
Jack A Lopez3 years ago
You've seen this picture: