I see a lot current forward on datasheet, but I don´t know the difference from the "normal" current.


On this datasheet, I saw a If (current forward) of 100mA and then on page 3 it states about current of 20mA. So, my question was about the difference of this two current.

  • 1
    \$\begingroup\$ What do you exactly mean by "normal" current? \$\endgroup\$ Jul 12, 2014 at 9:14
  • \$\begingroup\$ At the datasheet there is the If current of 100mA, and another current of 20mA \$\endgroup\$ Jul 12, 2014 at 16:24
  • \$\begingroup\$ Well provide a link to the datasheet then! I suspect you are referring to average and peak current, but without a specific question or a datasheet answer properly is impossible. \$\endgroup\$ Jul 12, 2014 at 16:43
  • \$\begingroup\$ Sorry, here is the link: everlight.com/datasheets/IR333_H0_L10_datasheet.pdf \$\endgroup\$ Jul 12, 2014 at 16:55
  • \$\begingroup\$ Page 3 uses a specific If as a condition for specifications; it does not describe a required or expected amount. \$\endgroup\$ Jul 12, 2014 at 20:44

2 Answers 2


Forward current (If) of a diode is the maximum safe current you can continuously pass through the device without causing it damage. The circuit is expected to limit the current through the device to this amount if there will be no pauses in the current (100% duty cycle). The parameter exists for IR LEDs, visible LEDs, and normal rectifiers, but the exact amount varies for each family as well as each specific model.


Forward current (If) is the manufacturers specifications of the maximum allowable current through the diode without damaging it by the use of a current limiting resistor if the voltage is above the diodes voltage rating. To calculate for the size of the current limiting resistor, subtract the diodes voltage specification from the source voltage then divide by the forward current, or less to get the required LED current limiting resistance value. For example, Vcc = 3V, Vled = 2V, and If led = 100mA Calculation: (15V - 2V)/0.100mA = 130 ohms

  • \$\begingroup\$ for consistency with example by user49219 ... solution should read Vcc = 3V, Vled = 2V, and If led = 100mA (3V - 2V)/0.100A = 10Ω \$\endgroup\$
    – lobsterman
    Jun 17, 2016 at 13:00

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