The Difference Between Avalanche Breakdown and Zener Breakdown
When a reverse-bias voltage is applied to a diode, it can undergo breakdown and allow current to pass through it. The two types of breakdowns that can occur in a diode are avalanche breakdown and zener breakdown. While both phenomena are caused by high reverse voltages, they differ in their mechanisms and characteristics.
Avalanche Breakdown
Avalanche breakdown occurs when a high electric field causes free electrons and holes to be accelerated to high speeds, and collide with other atoms in the diode. If the collision results in the release of additional free electrons, the process can become self-sustaining and lead to an exponentially increasing current flow. This is known as avalanche breakdown.
Avalanche breakdown typically occurs in high-voltage diodes and is characterized by a gradual, continuous increase in current with a small increase in reverse voltage. It can be modeled as a negative resistance, meaning that the voltage across the diode decreases as the current increases.
Zener Breakdown
Zener breakdown occurs when the electric field at the junction becomes high enough to cause the quantum mechanical tunneling of electrons through the depletion region of the diode. This process leads to the creation of a large number of electron-hole pairs, which results in a sharp increase in current flow.
Zener breakdown typically occurs in low-voltage diodes and is characterized by a sudden, sharp increase in current with a small increase in reverse voltage. It can be modeled as a voltage-controlled voltage source, meaning that the voltage across the diode remains relatively constant as the current varies.
Differences between Avalanche and Zener Breakdown
Avalanche breakdown and zener breakdown differ in several ways:
1. Mechanism: Avalanche breakdown is caused by collision of electrons and holes while zener breakdown is caused by quantum mechanical tunneling of electrons.
2. Voltage Range: Avalanche breakdown occurs in higher reverse voltages while zener breakdown occurs in lower reverse voltages.
3. Characteristics: Avalanche breakdown is characterized by a gradual, continuous increase in current with a small increase in reverse voltage, while zener breakdown is characterized by a sudden, sharp increase in current with a small increase in reverse voltage.
4. Applications: Avalanche breakdown is commonly used in high-voltage diodes for voltage regulation, while zener breakdown is commonly used in low-voltage diodes for voltage references.
In summary, avalanche breakdown and zener breakdown are two different phenomena that occur in diodes when subjected to high reverse voltages. Understanding the differences between them can help in choosing the right diode for a specific application.
Table difference between avalanche breakdown and zener breakdown
| Avalanche breakdown | Zener breakdown | |
|---|---|---|
| Definition | Occurs due to the ionization of the atoms in a reverse-biased PN junction under high electric fields | Occurs when the electric field exceeds a critical value in a heavily doped PN junction |
| Cause | Can be caused by thermal energy or high-voltage spikes | Occurs due to the heavy doping of the PN junction |
| Current direction | Current flows in both directions | Current flows in the forward direction |
| Effect on breakdown voltage | Increases as temperature increases | Remains constant over a wide range of temperatures |
| Applications | Used in high-voltage power supplies, lightning arrestors, and surge protectors | Used in voltage regulators, noise filters, and frequency multipliers |