Why Does a Zener Diode Withstand Reverse Biasing When Ordinary Diodes Fail?

[jobsism]

Hey everyone! I was just wondering why a Zener diode doesn't get damaged whereas an ordinary p-n junction diode does, when reverse-biased under sufficient voltage. In both diodes, when reverse-biased, there is a dislodging of valence electrons of the host atom. So, why does this damage the p-n junction diode alone, while the Zener diode remains safe?

 

[Antiphon]

The Zener can be destroyed by overheating due to too much current or inadequate cooling or both.

The ordinary diode also breaks down just like a Zener but is typically in a circuit that isn't designed to limit the breakdown current. In this case the diode is also destroyed by too much breakdown current.

If you take an ordinary diode and limit the current it will not be destroyed by exceeding the breakdown voltage.

 

[Drakkith]

See here: http://en.wikipedia.org/wiki/Zener_diode

It explains most of it in the first few paragraphs.

 

[Studiot]

I was just wondering why a Zener diode doesn't get damaged whereas an ordinary p-n junction diode does, when reverse-biased under sufficient voltage.

Whatever makes you think that?

Of course it does, if anything the situation is the other way round.

When we connect a diode in zener mode we always use a current limiting resistor (or source) in series.
If we don't do this, excess current will flow and destroy our diode.

When we connect a diode as a rectifier we employ one with a high enough blocking rating to prevent breakdown and reverse current flowing, thus there is no need for a current limiting resistor.

go well

 

[PJC01]

I can provide an explanation for why a Zener diode does not get damaged while an ordinary p-n junction diode does when reverse-biased under sufficient voltage.

Firstly, it is important to understand the difference between a Zener diode and a p-n junction diode. A Zener diode is specifically designed to operate in the reverse breakdown region, while a p-n junction diode is not. This means that a Zener diode is able to handle large amounts of reverse voltage without getting damaged.

Now, let's look at the mechanism behind reverse-biasing a diode. When a diode is reverse-biased, the majority carriers (electrons in an n-type material and holes in a p-type material) are pushed away from the junction, creating a depletion region. This depletion region acts as a barrier to current flow.

In a p-n junction diode, if the reverse voltage is high enough, it can cause the depletion region to break down and allow current to flow in the reverse direction. This current flow can lead to thermal runaway and damage the diode.

However, in a Zener diode, the doping levels are carefully chosen to create a very thin depletion region. This allows for a lower breakdown voltage and prevents thermal runaway. In addition, Zener diodes are designed to have a larger depletion region than p-n junction diodes, making them more resistant to breakdown.

In summary, a Zener diode is able to handle reverse bias because of its specific design and doping levels, which prevent thermal runaway and damage. This makes it an "invincible" diode in terms of reverse voltage protection.