The Difference Between Avalanche and Zener Breakdown
When it comes to the behavior of a diode, understanding its breakdown characteristics is critical. Two types of breakdowns are observed in diodes – avalanche and zener breakdowns. Although both are essential, there are some significant differences between them.
Avalanche Breakdown
Avalanche breakdown happens when the voltage applied to a diode exceeds a certain critical level. This critical voltage is known as the avalanche voltage. When the voltage exceeds the avalanche voltage, the electrons in the atoms of the p and n layers gain a high amount of energy, and they collide with other atoms, creating new holes – electron pairs. These newly created pairs can also gain high energy levels and initiate the same collision with other atoms.
This multiplication process continues, and a large number of electron-hole pairs are generated in a short period. The multiplication of charges results in a rapid increase in current through the diode. If the current is not limited by an external circuit, it can damage the diode.
Avalanche breakdown occurs in diodes that are constructed using materials like silicon, germanium, etc. These diodes have wider depletion regions and lower doping concentrations.
Zener Breakdown
Zener breakdown occurs when the reverse-bias voltage applied to a diode exceeds a certain threshold value, known as the zener voltage. Unlike avalanche breakdown, zener breakdown is not associated with the collision of atoms. Instead, when the reverse-bias voltage applied to the diode is higher than the zener voltage, the depletion region’s width decreases, allowing current to flow across the junction.
In the zener breakdown, the diode acts as a voltage regulator. It is frequently used in voltage reference circuits, where the output voltage is controlled by the zener diode. Zener diodes are constructed using heavily-doped p-n junctions that are designed to have a narrow depletion region.
Conclusion
In summary, avalanche and zener breakdowns are two critical properties of diodes. The avalanche breakdown occurs in diodes with wider depletion regions, while zener breakdown occurs in diodes with narrow depletion regions that are designed for such operations. Understanding the differences between these two types of breakdowns can help electrical engineers and designers select the appropriate diode for different applications.
Table difference between avalanche and zener breakdown
| Parameter | Avalanche Breakdown | Zener Breakdown |
|---|---|---|
| Definition | Occurs due to the collision of electrons with atoms in a reverse-biased junction. | Occurs due to the electric field intensity that exceeds the breakdown voltage level in a heavily doped p-n junction. |
| Symbol | Va | Vz |
| Type of breakdown | Unpredictable and sudden | Predictable and controlled |
| Current | Higher current flows | Lower current flows |
| Output | Produces noise and possible destruction of the device | Produces a stable voltage reference |
| Applications | Not used as a voltage reference | Used as a voltage reference in voltage regulators and power supplies |