LEDs Can Be Driven Directly From A Voltage Source

Not Recommended

It is not recommended to apply a direct voltage source to an LED without a current limiting resistor or source even though the LED appears to be functioning correctly.

As illustrated in the typical Current (If) Vs. Forward Voltage (Vf) graph above, a slight change in Vf will cause a large change in If. This can result in a possible over-drive condition, thus reducing the life and/or reliability of the LED. Even if over-drive conditions are not reached, large variations in If will result in significant luminous intensity variation. The preferred method of operating from a voltage source is via a series resistor to limit the current flow through the LED.

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