I have been trying to find out the characteristic differences between Zener and Avalanche Diodes. They appear to be very similar but I would like to know what the key operational differences are and why you would choose one over the other. Most sites found on google and videos on Youtube only talk about the molecular difference which does not really give me the answers.

Would much appreciate any guidance on this.

 

Above might help.

Regards, Dana.

 

Above might help.

Regards, Dana.

Thanks, but I had already viewed these. They talk about the atomic science and doping etc but I am still uncertain about the real world applications for each. When would you use an Avalanche diode rather than a Zener diode and why?

 

To put it simply, if you want a low voltage device (I think the split is around 4.7 volts) use a Zener diode. Higher voltage devices are avalanche diodes.

My distributor does not differentiate. Zener and Avalanche diodes as are all lumped into the category "Zener diode". We use the same symbol for both because functionally they are very similar.

 

I have been trying to find out the characteristic differences between Zener and Avalanche Diodes. They appear to be very similar but I would like to know what the key operational differences are and why you would choose one over the other.

I think you'll find the answer in this application note.

We don't "choose" one or the other; zener diodes rated below about 5 volts operate via the zener breakdown mechanism while those above 8 volts operate via avalanche breakdown. In between, both mechanisms are involved.

Regardless of which breakdown mechanism predominates, we call all such diodes "zener diodes."

 

I think you'll find the answer in this application note.

We don't "choose" one or the other; zener diodes rated below about 5 volts operate via the zener breakdown mechanism while those above 8 volts operate via avalanche breakdown. In between, both mechanisms are involved.

Regardless of which breakdown mechanism predominates, we call all such diodes "zener diodes."

Ah OK! Many thanks. I thought these were two different type of components.

 

In essence, both processes take place at the same time, but at low voltages zener breakdown dominates and at higher voltages avalanche dominates.

But a very useful property emerges as a consequence.

In zener breakdown, the voltage has a negative temperature coefficient, but in avalanche breakdown the voltage has a positive tempco. Thus, not surprisingly, there is a sweet spot at which the two processes are in rough balance and the opposing temperature coefficients effectively cancel out, resulting in a device that have extremely low temperature coefficient. This voltage is usually just below 5 V, so designers that want a cheap way to minimize tempco effects will try to use 4.7 V or 5.1 V zener diodes. This is not the end-all-be-all, of course, as there are other factors at play, as well.