I have a RL80-UR543 LED 8MM. How much voltage I need if I use a resistor of 100Ohm?


1 Answer 1


Forward Current (If) = 20 mA and

Forward Voltage (Vf) = 1.7V to 2.8V
is written on datasheet

  • maximum voltage = 20mA*100ohm + 2.8V = 4.8V
  • \$\begingroup\$ I conntect it to a battery without any resistor and nothing happened. Bettery is 1.5v \$\endgroup\$
    – No Namer
    Jan 8, 2019 at 20:31
  • \$\begingroup\$ I calculated theoretical maximum voltage according to your requirements. Using leds without current control not a good way. \$\endgroup\$
    – Koray
    Jan 9, 2019 at 5:56

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