modify the optocoupler that use NPN t

Discussion in 'Embedded Systems and Microcontrollers' started by mermaid09, Dec 12, 2009.

  1. mermaid09

    Thread Starter New Member

    Nov 21, 2009
    Hai looking to modify the optocoupler that use NPN transistor like in below diagram.

    My aim is to modify above circuit to become optocoupler that same funtion as optocoupler that use phototransistor. My question here is
    - if the base of NPN transistor in not to connect to any compenent(opened based), are there same function like photoransistor?
    - if yes, i want to build the above circuit ( at part NPN transistor) to become darlintong circuit without use the base pin at pin 6. Then what suitable transistor that i should choose?i will use 12 V DC supply voltage to darlington circuit.

  2. hgmjr


    Jan 28, 2005
    Is your goal to modify a simulation model or are you wanting to modify actual circuitry?

    Under most circumstances, you can leave the base unconnected.

  3. mermaid09

    Thread Starter New Member

    Nov 21, 2009
    tq for reply..i`m only to modify a simulation model..then i don`t know how to choose the correct type of transistor to become as darlington circuit. I don`t know what type of the transistor that use in the internal diagram, so i can`t match the transistor.
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    You might search for an opto isolator with a photodarlington output.