Avalanche diodes and Zener diodes are both types of semiconductor diodes that operate in the reverse-biased mode, but they have distinct characteristics and applications due to their different operating mechanisms. Let's discuss the key differences between these two diodes:
Zener diode: Zener diodes are designed to operate in the reverse breakdown region, which is also known as the Zener region. When the reverse bias voltage across a Zener diode exceeds its Zener voltage (also called breakdown voltage or avalanche point), the diode enters the breakdown region, and a controlled current flows through the diode, allowing it to regulate voltage.
Avalanche diode: Avalanche diodes, on the other hand, also operate in the reverse breakdown region but rely on a different mechanism. When a high reverse bias voltage is applied to an avalanche diode, the electric field across the depletion region becomes strong enough to cause impact ionization. This generates electron-hole pairs, resulting in an avalanche effect, and a large current starts flowing through the diode.
Zener diode: Zener diodes exhibit a sharp breakdown characteristic. Once the Zener voltage is reached, the voltage remains nearly constant, and the diode can efficiently regulate the voltage across its terminals.
Avalanche diode: Avalanche diodes have a more gradual breakdown characteristic. As the reverse voltage increases, the current also increases, but the voltage drop across the diode rises less sharply than in Zener diodes.
Zener diode: Zener diodes are primarily used for voltage regulation and voltage reference applications. They can maintain a nearly constant voltage across their terminals, even when the input voltage fluctuates or when subjected to varying loads. They are commonly employed in power supplies, voltage regulators, and protection circuits.
Avalanche diode: Avalanche diodes find applications in areas that require overvoltage protection. Due to their ability to handle higher power dissipation during breakdown, they are often used in surge protection devices, inductive load clamps, and high-voltage transient suppression circuits.
Zener diode: Zener diodes typically have a more precise breakdown voltage tolerance, which is critical in voltage regulation applications. The tolerance is usually within a few percentage points.
Avalanche diode: Avalanche diodes generally have a wider tolerance range for breakdown voltage, which might be sufficient for applications involving transient voltage protection.
In summary, Zener diodes are primarily used for precise voltage regulation and reference applications, while avalanche diodes are chosen for their ability to handle high-power dissipation during breakdown and are utilized for overvoltage protection and transient suppression applications. It's important to select the appropriate diode based on the specific requirements of the circuit or system being designed.