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Zener diode structure and working principle - Database & Sql Blog Articles
The Zener diode shares a similar basic structure with a regular diode, as it is also a PN junction. However, due to specialized manufacturing techniques, the Zener diode can withstand reverse breakdown without being damaged. This unique property makes it ideal for voltage regulation applications. Unlike standard diodes, which are primarily used for rectification, Zener diodes operate in the reverse breakdown region to maintain a stable voltage.
When the reverse voltage applied to a Zener diode reaches a specific threshold, known as the Zener voltage, a significant reverse current begins to flow. Despite this increase in current, the voltage across the diode remains nearly constant. This phenomenon is referred to as tunnel breakdown and is commonly used in low-voltage Zener diodes (typically below 5V). For higher voltages, the breakdown mechanism shifts to avalanche breakdown, where a strong electric field causes the current to rise rapidly while maintaining a stable voltage. This is more common in silicon Zener diodes operating above 7V.
The U-I characteristic curve of a Zener diode illustrates its voltage regulation behavior. In the forward bias region, the curve resembles that of a regular diode, with a gradual increase in current as voltage rises. However, in the reverse bias region, the curve becomes steep at the Zener voltage point, indicating that even small changes in current result in minimal voltage fluctuations. This stability is crucial for its use in power supply circuits.
The Zener voltage, denoted as UZ, represents the stable voltage level at which the diode operates in breakdown mode. Different Zener diodes have varying UZ values depending on their design and application. It's important to ensure that the current flowing through the diode does not exceed its maximum rated value, as excessive current can lead to overheating and damage.
In temperature-sensitive applications, a special type of Zener diode called a temperature-compensated Zener is used. This design incorporates two Zener diodes connected in opposite directions. One diode operates in the forward bias, while the other is in reverse bias. As temperature changes, the voltage drops across each diode change in opposite ways, effectively canceling out the temperature effects. This ensures a more stable output voltage over a wide temperature range.
Additionally, the direction of current flow in a Zener diode is different from that of a regular diode. While a normal diode allows current to flow from the anode to the cathode, a Zener diode conducts in the reverse direction when in breakdown mode. This distinction is essential for proper circuit design and functionality.
By understanding these characteristics, engineers can effectively utilize Zener diodes in various electronic circuits, especially where voltage stabilization is required.