Minimum current for 4N26 optocoupler

Discussion in 'Homework Help' started by Jack Kotze, Mar 18, 2009.

  1. Jack Kotze

    Thread Starter New Member

    Mar 3, 2009
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    0
    What is the minimum forward current to ensure that the transistor will turn on in a 4N26 optocoupler? The datasheet shows that the typical forward voltage is 1.18v @ 10mA. Is 10mA enough?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    There is a transfer curve for the 4N26.
    The collector current of the transistor depends on the current in the LED.

    [​IMG]

    The text sample A and sample B expains the marges of spreading.

    Greetings,
    Bertus
     
  3. Jack Kotze

    Thread Starter New Member

    Mar 3, 2009
    7
    0
    What's the difference between Sample A and Sample B?

    If I'm getting this, then based on Sample A, a forward led current of 10mA will "bias" the transistor just enough to pass slightly more than 10mA? Not sure if "bias" is the right word?

    I was thinking of using the 4N26 as a switch on the output of a monostable 555 circuit. The output will be used to close the shutter of a digital camera. Do I need to measure the voltage drop when the camera's switch is open and the current when it's closed?

    Thanks for the help.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    The difference between Sample A and Sample B is the difference in specifications that can will happen during the production.
    If you want to have a optocoupler that fuctions with higher tranfer gain, take a look at the SFH620A - 3.

    Greetings,
    Bertus
     
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