<P> Most LEDs have low reverse breakdown voltage ratings, so they will also be damaged by an applied reverse voltage above this threshold . The cause of damage is overcurrent resulting from the diode breakdown, not the voltage itself . LEDs driven directly from an AC supply of more than the reverse breakdown voltage may be protected by placing a diode (or another LED) in inverse parallel . </P> <P> The manufacturer will normally advise how to determine the polarity of the LED in the product datasheet . </P> <P> Many systems pulse LEDs on and off, by applying power periodically or intermittently . So long as the flicker rate is greater than the human flicker fusion threshold, and the LED is stationary relative to the eye, the LED will appear to be continuously lit . Varying the on / off ratio of the pulses is known as pulse - width modulation . In some cases PWM - based drivers are more efficient than constant current or constant voltage drivers. . </P> <P> Most LED data sheets specify a maximum DC current that is safe for continuous operation . Often they specify some higher maximum pulsed current that is safe for brief pulses, as long as the LED controller keeps the pulse short enough and then turns off the power to the LED long enough for the LED to cool off . </P>

What is the maximum current for a led