voltage limiter problem

Discussion in 'The Projects Forum' started by studystudystudy, Jul 14, 2010.

  1. studystudystudy

    Thread Starter Member

    May 21, 2010
    i using two zener diode having 5V breakdown voltage as a limiter

    two zener diode is parallel with each other but the one of the zener diode polarity is inverse.

    if i connect to the input AC voltage, its should limit the voltage to 5V if the input is exceed 5 voltage.

    i simulate it in the Multisim, but the output always same with the input no matter the input value is exceed or lower the breakdown voltage.

    why this happen?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    It may be because Zeners operate in reverse polarity. If forward biased, they work like ordinary diodes. Is the voltage clamped at about +/-700 mv?
  3. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    As beenthere stated zeners work in reverse bias. If you want to limit the voltage of an AC signal to 5V you would need to put the in series but back to back. That way one will be forward biased and the other reversed. When the signal goes in the opposite direction the opposite diodes will conduct.
  4. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    With regards to your original post, what AC voltage are you applying in your simulator?