Take the 2-minute tour ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.

I was wondering whether there is a difference between Zener effect and Avalanche effect? How do they differ?

share|improve this question
    
Third result for a google search of "avalanche diode": Zener and Avalanche Breakdown/Diodes –  Phil Frost Jan 14 '13 at 14:26

1 Answer 1

up vote 5 down vote accepted

There are two entirely different effects exploited in zener diodes; at low voltages, the effect is tunnelling across the junction, and at higher voltages, the effect is identical to the avalanche diode. The temperature coefficient of each effect is different; I can't find my reference offhand but one (I think tunnelling) the zener voltage decreases with temperature and the other effect has an increasing voltage with temperature.

The importance of this detail is that zener diodes around 5.6 or 6.2 volts have close to zero temperature coefficient of voltage, since in that voltage range, both effects are equally important.

Edit : "zener breakdown" at low voltages may not be tunnelling as I (mis?-)remembered; however it is a separate effect from avalanche breakdown. I did get the temperature dependence right way round though.

Wikipedia suggests the difference is this : in the zener effect, the electric field across the junction breaks bonds to release carriers; while in the avalanche effect it is collisions which break bonds and release carriers.

On the other hand, this article does use the words "quantum tunnelling" to describe the Zener effect, so maybe I'm not completely senile yet...

share|improve this answer
    
No, not completely :-) –  Anindo Ghosh Jan 14 '13 at 13:21
    
Yes - tempco for Zener effect is negative and for avalanche effect it is positive. –  LvW Sep 29 at 20:19

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.