Zener diode

Discussion in 'Homework Help' started by JoyAm, Sep 10, 2014.

  1. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    Hello,
    There is a problem when i am asked to calculate the current that flows through a zener diode as well ass the voltage of the output. Also i am asked to check if the diode is indeed in the zener zone, i calculated the first two values but i dont know how to check if the diode is on zener
    Screenshot_4.png Screenshot_5.png
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    At first, ignore the value of R2 and assume that the zener diode is not conducting.
    Calculate the voltage across RL using standard voltage divider equation.
    This will establish if the zener voltage has been exceeded.
     
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  3. dalam

    Member

    Aug 9, 2014
    58
    6
    Zener diode is in breakdown region. Because if you consider that it is reverse biased and make it open circuit you will get a voltage of 10 around it. And it requires 5v to enter into saturation so it is in breakdown region.
    Your values of Iz is correct.
     
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  4. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    This way the voltage at RL is 10 volts so it has exceeded it by double. That means that the diode is indeed working on zener because it keeps the output voltage at around 5 volts when we assume it works this way ?
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    Are you calling V2 the zener diode?

    On edit ... my mistake. I see it is Vz on the schematic.
     
    Last edited: Sep 10, 2014
  6. dalam

    Member

    Aug 9, 2014
    58
    6
    If you want to check if any diode is on or off consider all possible case and check which combination is satisfying the circuit. Only one should do it.
     
  7. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    My handwriting is confusing you here i guess what you see as V2 and R2 were supposed to be Vz and Rz so yes this is the zener sir.

    Yeah thats true but it will not tell me if its specific in zener, right ?
     
  8. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,962
    1,097
    Exactly, and this is true, only if Zener diode is connected in property way.
     
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