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I have some blue LEDs that are listed at having a Vf of 3.3V @ 20mA. If I want to drive them from a 3.3V source, do I need a dropper resistor? Methinks I do, but R = (3.3 - 3.3) / 0.02 = 0 Ohms!

I know that LEDs can be finicky about how they're driven, so is there a rule of thumb? (There's no data sheet as they're unbranded.)

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  • \$\begingroup\$ No datasheet; No sale! =-D \$\endgroup\$
    – Tyler
    Commented Apr 5, 2019 at 23:03
  • \$\begingroup\$ Boost the voltage and then use a resistor? LED Driver? You don't specify efficiency and cost requirement, so I guess that's fine. I think this type of question is somewhat funny puzzling. \$\endgroup\$
    – Unknown123
    Commented Apr 5, 2019 at 23:28
  • \$\begingroup\$ What purpose do you want to drive these LEDs? To illuminate the entire room, or something else? And what kind is your "a 3.3V circuit"? A GPIO of a MCU, or a 5-mOhm MOSFET? \$\endgroup\$
    – Ale..chenski
    Commented Apr 5, 2019 at 23:37
  • \$\begingroup\$ @Ale..chenski The duplicate wasn't recognised when I wrote the question. Thanks. \$\endgroup\$
    – Paul Uszak
    Commented Apr 5, 2019 at 23:42

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