+ Post New Thread
Results 1 to 4 of 4
  1. #1
    Advanced Member level 1
    Points: 4,398, Level: 15

    Join Date
    Jul 2006
    Location
    USA
    Posts
    411
    Helped
    8 / 8
    Points
    4,398
    Level
    15

    forward voltage of LED diode

    I found all the LED diode have a minimal forward voltage of 1.7V. Anyone knows that whether there are some LED diode with forward voltage less than 1V, and the forward current is less than 20mA? Thank you.

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 15,218, Level: 29
    schmitt trigger's Avatar
    Join Date
    Apr 2013
    Posts
    2,529
    Helped
    813 / 813
    Points
    15,218
    Level
    29

    Re: forward voltage of LED diode

    Forward voltage drop depends on the LED wavelength.
    IR diodes indeed have forward voltages of around 1.7 volt, blue diodes are over 3 volts.

    But less than 1 volt?
    No.
    My batteries are recharged by "Helpful Post" ratings.
    If you feel that I've helped you, please indicate it as a Helpful Post


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  3. #3
    Advanced Member level 1
    Points: 4,398, Level: 15

    Join Date
    Jul 2006
    Location
    USA
    Posts
    411
    Helped
    8 / 8
    Points
    4,398
    Level
    15

    Re: forward voltage of LED diode

    Oh, that is the reason. Thank you.



    •   AltAdvertisement

        
       

  4. #4
    Advanced Member level 5
    Points: 18,428, Level: 32
    Achievements:
    7 years registered

    Join Date
    Nov 2012
    Posts
    3,267
    Helped
    815 / 815
    Points
    18,428
    Level
    32

    Re: forward voltage of LED diode

    Anyone knows that whether there are some LED diode with forward voltage less than 1V, and the forward current is less than 20mA?
    Current is not the issue, it is the voltage drop. That is the barrier energy.

    Say you have a forward drop of 1V. One electron crossing the barrier will get an energy of 1 eV - this is in energy terms approx 1.2um wavelength of light.

    See for more information https://en.wikipedia.org/wiki/Photon_energy

    And this is assuming 100% efficiency. If you have an IR LED, the minimum voltage drop will be around 1.3V (100% efficiency) to get a photon of 1000nm wavelength (typical for IR LEDs).

    If you want 500nm wavelength, you will need a larger voltage drop: about 2.6V.

    Add about 100-300mV extra for other losses.


    1 members found this post helpful.

--[[ ]]--