Zener Diode explained

Discussion in 'General Electronics Chat' started by Abhinavrajan, Sep 9, 2016.

  1. Abhinavrajan

    Thread Starter Member

    Aug 7, 2016
    I have read the zener diode.
    It acts as a voltage regulator.

    In the Zener diode V-I characteristics,
    After the zener breakdown, the voltage remains constant at the breakover voltage while allowing enormous amount of current through it.
    The voltage simply doesnt increase or decrease after attaining the zener breakdown but current can increase to a very high value or even a very low value.

    But, how can a device allow enormous amounts of current through it while maintaining the voltage across it at a constant value?
    What happens inside the zener diode after the breakdown voltage?
    Please explain the internal structure after zener breakdown.
    Thanks! :)
  2. crutschow


    Mar 14, 2008
    Define "enormous".

    I think you have an idealized view of how a Zener diode works.

    A Zerner can only carry a maximum current as determined by its power rating stated in its data sheet.
    The power dissipated in the Zener is the current times the zener breakdown voltage.

    Thus a 5V, 500mW zener could carry only a maximum current of 0.5W/5V = 0.1A at 25°C ambient.
    I wouldn't call that "enormous".

    Also the voltage isn't completely constant. It varies by the current change times the zener dynamic resistance, Zzt (also in data sheet). when in breakdown.
    MrSoftware and Abhinavrajan like this.
  3. Abhinavrajan

    Thread Starter Member

    Aug 7, 2016
    Yeah. Sorry. But how does the voltage across remain constant after its breakdown?
    Please explain what happens to the internal structure of zener during and after the zener breakdown.
  4. Rodney Phillips

    New Member

    Jun 12, 2015