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zener diode

Discussion in 'General Electronics Discussion' started by niyaz432, Sep 1, 2015.

  1. niyaz432

    niyaz432

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    Aug 31, 2015
    Hi Guys... How exactly zener diode used as voltage regulator... if i want to vary or change the voltage i will change the value of resistor. what is the use of zener diode in the below circuit. can you please explain. Vs=10V , R1=200 ohms
    example1.png
     
  2. Old Steve

    Old Steve

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    Jul 23, 2015
    The Zener diode will have a voltage rating. Let's assume it's a 4.7V Zener.
    The output of the first circuit will be 4.7V
    The output of the second circuit will be 6V.
    ie (10V / (300 +200)) x 300
     
  3. niyaz432

    niyaz432

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    Aug 31, 2015
    Thanks for your reply, But what is the use of zener diode...i will always use second circuit to vary my voltage...i will change the resistance value from 300 ohms to 400 ohms or 100 ohms as per requirement.
    But practically zener diode will use as voltage regulator . I am not getting this one
     
  4. Old Steve

    Old Steve

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    Jul 23, 2015
    A Zener can be used a a low current shunt regulator as shown or it can provide a reference voltage that remains reasonably constant when the supply voltage changes, or it can be used as protection to keep a point in a circuit from going higher than a given voltage.

    If your 10V supply was not regulated and varied between 8V and 12V, for instance, the Zener would keep the output at approximately 4.7V, (if a 4.7V Zener is used).
     
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  5. Harald Kapp

    Harald Kapp Moderator Moderator

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  6. davenn

    davenn Moderator

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    good explanation, Old Steve

    Dave
     
  7. niyaz432

    niyaz432

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    Aug 31, 2015
    it means that if any fluctuations in my supply voltage ,by using zener diode i can ge
    Thanks a Lot.
    It means that any voltage fluctuations in supply voltage , may be will not get required output voltage, so we need to use zener diode.
    if i want to maintain my output voltage 4.7V or 5V i need to choose a zener diode which is having VZ=5.0V or VZ=4.7V rating, so my output voltage will be always 4.7v or 5v.
     
  8. Old Steve

    Old Steve

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    Jul 23, 2015
    Thanks Dave.
     
  9. davenn

    davenn Moderator

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    yup, exactly
     
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  10. Old Steve

    Old Steve

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    Jul 23, 2015
    Yes. Keep in mind, though, that a Zener is only a crude regulator, and it's voltage will vary slightly with changes in supply voltage or with changes in load. Check out Harald's link. It has good info on the subject.
     
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  11. Harald Kapp

    Harald Kapp Moderator Moderator

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    An improved version of a zener diode stabilizing circuit uses a transistor to decouple the load current from the current through the zener diode, see e.g this article.
     
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