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zener diodes

Discussion in 'General Electronics Chat' started by idsinc, Dec 9, 2011.

  1. idsinc

    idsinc New Member

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    | | 0V
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    What does it mean when zener diodes are put anode to anode in a circuit? Wish I could insert a jpg. Makes it easier to communicate.
     
  2. idsinc

    idsinc New Member

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    Took out the extra junk. one side is +VDC, the other side is 0V.
     
  3. Dragon Tamer

    Dragon Tamer Member

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    You can insert .jpg files into your posts, you have to go to the advanced option.

    What the zener is doing in the circuit is basically surge suppression. When you have two connected anode to anode, then they are acting as surge suppression for either AC or reversed polarity DC.
     
  4. dave

    Dave New Member

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  5. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    Attached is an image of what it looks like with back to back zener diodes acting as a clipping circuit. Assume the zener diodes to be 10 volt zener diodes and a 20 volt peak AC waveform is applied. The green trace is the full AC signal at the source and the red trace is measured between the top of D1 and Ground. Hope the cartoon helps.

    Ron
     

    Attached Files:

  6. ljcox

    ljcox Well-Known Member

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    It creates a symmetrical Zener diode.

    If both Zeners are say 10 Volt ones, then when you connect them in inverse series, they become a symmetrical Zener of about 10.7 Volt.

    So it can be used for surge suppression, do clipping of AC signals as above or be used in any situation where a symmetrical Zener is required.

    You can create .gif circuits by drawinmg them in PowerPoint & saving them as .gif.

    Alternatively, you can draw them in Paint or other bit map software.
     
    Last edited: Dec 9, 2011
  7. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Or, you can just look at Ron's post #4 above :)
     
  8. idsinc

    idsinc New Member

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    Thank you all. That was very helpful.
     
  9. ljcox

    ljcox Well-Known Member

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    You're welcome.

    Its nice when some appreciation for our effort is shown by the OP.

    Some don't bother &, in those cases, I'm left wondering why I bothered.
     
  10. clel miller

    clel miller Member

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    Interesting......
    Besides maybe audio.....what application would this be for.?
    Thanks
     
  11. unclejed613

    unclejed613 Well-Known Member

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    it could be used in audio as a clipping circuit (or clamping), for instance to "pre-clip" an audio signal before an amplifier, to protect the amplifier from input stage damage. some amplifiers (especially op amps) can be damaged if the input voltage exceeds the rail voltages. in many receiver designs, the inputs go to either op amps or CMOS selector switches, which might be damaged by voltage surges or even static electricity, and the zeners clamp the voltage to a safe level. there have also been amplifiers that use such a circuit at the input to clip the waveform slightly below the voltage required to saturate the output stage of the power amp. by keeping the output stage out of saturation, the amplifier and it's feedback loop don't "misbehave". the side effects of saturation can sound much worse than the clipped signal itself (as well as damaging tweeters). the technique is called "soft clipping"
     
    Last edited: Dec 13, 2011
  12. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    In general circuit protection or if you are very poor a poor man's square wave generator? :)

    Seriously, circuit protection. In the little cartoon I posted if Vin for example was below 5 volts peak nothing would happen and the signal would be passed. Only when the circuit exceeded the zener breakdown voltage did the clipping happen.

    Ron
     
  13. clel miller

    clel miller Member

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    Got it......Thanks
    And yeah.....
    "soft" clipping.....another interesting application. I pretty much only look at tubes, so we do not see diodes in the signal path too often. Kind of an abomination....wheteher it is real or imagined. :)
    Thanks Again
     

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