Introduction To Avalanche Voltage

If you are an engineering student or an engineer, you probably know how important voltage is in electronics.

But what about avalanche voltage? This interesting thing happens when a pn semiconductor junction has a sudden increase in current, which causes the material to break down.

Even though it sounds like a destructive force, avalanche breakdown is now an important part of many electronic devices, such as photodiodes and Zener diodes.

Understanding avalanche voltage and how it can be used in real life can be a game-changer for engineers and help them make better, more efficient designs.

So, come along with us as I talk about the fascinating world of avalanche voltage and how it affects the field of engineering.

Formal definition:

The reverse voltage required to cause avalanche breakdown in a pn semiconductor junction.

Avalanche Voltage and Depletion Layer Width

Avalanche voltage is the voltage at which avalanche breakdown happens in a p-n junction diode.

When a reverse bias is put on a lightly doped p-n junction, the electric field speeds up the electrons in the depletion layer, giving them a lot of speed.

This energy can cause ionization of atoms in the crystal lattice, resulting in a large current flow.

Relationship between Depletion Layer Width and Avalanche Voltage

The avalanche voltage of a diode is related to the width of the depletion layer in a semiconductor junction.

The part of the p-n junction where there are no free charge carriers is called the depletion layer.

It is made when minority carriers move across the p-n junction. This makes a region with a net charge that stops more minority carriers from moving.

How wide the depletion layer is depends on the amount of doping and the bias voltage that is used. Diodes with high breakdown voltages are lightly doped, which makes depletion layers that are wide.

Diodes with low breakdown voltages, on the other hand, are heavily doped, which makes depletion layers that are narrow.

The avalanche voltage will be greater if the depletion layer is bigger. This is because wider depletion layers have a bigger electric field, which speeds up electrons to faster speeds.

This causes more electrons to become ions, so the breakdown voltage is higher.

Design Considerations

When making p-n junction diodes, it is important to think about the relationship between the avalanche voltage and the width of the depletion layer.

A diode with a high breakdown voltage is useful for many things, like regulating voltage and reversing the flow of power.

To achieve a high breakdown voltage, the depletion layer must be wide, which can be accomplished by using lightly doped semiconductor material.

In short, avalanche voltage is the voltage at which avalanche breakdown causes a p-n junction diode to break down.

The avalanche voltage is linked to the width of the depletion layer because it affects the voltage at which the diode breaks down.

Understanding the relationship between the avalanche voltage and the width of the depletion layer is important for designing and optimizing p-n junction diodes for different uses.

Avalanche Breakdown in PN Semiconductor Junctions

Avalanche breakdown is a process that happens when the reverse voltage across a lightly doped p-n junction is higher than a certain level, called the breakdown voltage.

At this voltage, the electric field at the junction is strong enough to push on the electrons and break them free from their covalent bonds.

The free electrons then hit other atoms in the device, releasing more electrons and causing an avalanche of current.

This is called "carrier multiplication," and it causes the flow of current through the p-n junction to increase significantly.

Mechanism of Avalanche Breakdown and Comparison with Zener Breakdown

Avalanche breakdown happens when free electrons and atoms in the device bump into each other.

Zener breakdown, on the other hand, is caused by a strong electric field across the p-n junction.

Both the avalanche breakdown and the Zener breakdown involve the creation and movement of electrons and holes inside the semiconductor material.

But the biggest difference between the two types of breakdown is how the electron-hole pair is made.

Differences between Avalanche and Zener Breakdowns

Avalanche breakdown is irreversible and happens at a higher reverse voltage than Zener breakdown.

The breakdown voltage is controlled by the amount of doping in the semiconductor material.

As the amount of doping goes up, both the avalanche method temperature coefficient and the size of the breakdown voltage go up.

Avalanche breakdown happens in materials with a small amount of doping, while Zener breakdown happens in materials with a lot of doping.

The junction of a diode will not go back to where it was after an avalanche breakdown, but it will go back to where it was after a Zener breakdown.

Avalanche breakdowns happen in thick parts of the semiconductor material, while Zener breakdowns happen in thin parts.

It is worth noting that both types of breakdown are not likely to happen at the same time.

Each type of breakdown is caused by different things, and it is unlikely that both will happen at the same time.

Video: Understanding the avalanche effect: an introduction

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Practical Applications of Avalanche Breakdown

Avalanche breakdown is a phenomenon that can happen in both insulating and semiconducting materials.

This is when a large current can flow through materials that are normally good insulators.

The process can be used in electronic devices to do useful things like stop surges, protect against overvoltage, use as a voltage reference, and make current sources.

Surge Suppression

In surge suppression circuits, avalanche breakdown is used to protect electronic devices from voltage spikes caused by lightning strikes, electromagnetic pulses, or other things.

In this case, the device to be protected is connected in parallel with an avalanche diode.

When the voltage across the device is higher than the diode's breakdown voltage, the diode goes into the avalanche breakdown region, which takes the extra voltage away from the device being protected.

This keeps the surge of electricity from hurting the device.

Overvoltage Protection Circuits

Avalanche breakdown is also used in circuits that protect electronic devices from being damaged by too much voltage.

In these circuits, the device to be protected is connected in series with an avalanche diode.

When the voltage across the device is higher than the diode's breakdown voltage, the diode goes into the avalanche breakdown region, which limits the voltage across the device being protected.

Voltage Reference Circuits

In voltage reference circuits, avalanche breakdown is used to make sure that the reference voltage is stable and accurate.

As a voltage reference, an avalanche diode with a backwards bias is used in these circuits.

The breakdown voltage of the diode is very stable and depends on how much doping is done when it is made. This makes it a great reference voltage for applications that require high accuracy.

Current Sources

Avalanche breakdown is used in current sources where a stable current is needed, such as in precision instrumentation and measurement circuits.

In these circuits, an avalanche diode is connected in series with a resistor.

The breakdown voltage of the diode and the value of the resistor determine how much current flows through the circuit.

Control and Prevention of Avalanche Breakdown

In electronic circuits, there are a number of ways to stop or control avalanche breakdown.

Avalanche Diodes

An avalanche diode is one way to stop an avalanche from breaking up. Avalanche diodes are made to work in the reverse breakdown region, and they are used to protect circuits from voltages that are not wanted.

The junction of an avalanche diode is made to break down evenly across the whole junction. This keeps current from concentrating and hot spots from forming.

In contrast to a non-avalanche diode, the breakdown voltage of an avalanche diode stays almost the same as the current changes.

Transient Suppression Devices and Voltage Clamping

Electronic circuits can also be made safe from avalanche breakdown with the help of transient suppression devices and voltage clamping.

Zener diodes are often used to clamp voltage.

When two zener diodes with the same reverse breakdown voltage are used, a transient voltage of either polarity will be clamped at the same zener voltage level.

MOSFETs

When a voltage is higher than the MOSFET's breakdown voltage, it can also go into an avalanche mode, which can cause problems.

Avalanche breakdown in MOSFETs can be avoided with good circuit design and careful choice of MOSFETs with the right voltage ratings.

Additional Ways to Prevent Avalanche Breakdown

There are more ways to stop avalanche breakdown in electronic circuits than just using avalanche diodes, transient suppression devices, voltage clamping, and careful choice of MOSFETs.

Here are some of them:

Voltage and Avalanche Breakdown

Dielectric Strength and Breakdown Voltage

The ability of a material to withstand electrical stress without breaking down and becoming conductive is measured by its dielectric strength. Volts per centimeter are a common way to measure it.

The chance of failure at this voltage is low enough that insulation can be made with the assumption that it will not break at this voltage.

AC breakdown voltages and impulse breakdown voltages are both ways to measure the dielectric strength of a material.

The AC voltage is the line frequency of the mains, while the impulse breakdown voltage imitates lightning strikes.

It usually takes the wave 1.2 microseconds to rise to 90% amplitude, then 50 microseconds to drop back down to 50% amplitude.

Conclusion

In conclusion, avalanche breakdown and voltage may seem like complicated ideas that only experts can understand, but they are both important parts of modern electronics.

By knowing how these things work and how they can be used in electronic devices, engineers can make designs that are more efficient and unique.

The study of avalanche voltage and breakdown may be even more important because it shows how powerful and useful electronics can be.

It is easy to take the tools and machines we use every day for granted, but it is amazing to think about the amazing forces at work inside them.

So, as you keep learning about engineering, do not forget to be amazed by the cleverness and creativity that go into making the technology we use every day.

Who can say? Maybe you will be the one to find the next big thing in avalanche breakdown or voltage, which will lead to even bigger things in the future.