Schottky diodes, known for their fast switching speed and low forward voltage drop, are widely employed in various electronic circuits. However, despite their advantages, they also exhibit certain disadvantages compared to conventional PN junction diodes. This article delves into the key drawbacks of Schottky diodes, providing a comprehensive understanding of their limitations and how they compare to their traditional counterparts.
Schottky Diode Disadvantage: Limitations and Trade-offs
Schottky diodes are renowned for their rapid switching characteristics and low forward voltage drop, making them ideal for high-frequency applications. However, these benefits come at a cost, as Schottky diodes also possess certain drawbacks compared to standard PN junction diodes.
Higher Reverse Leakage Current
One significant disadvantage of Schottky diodes is their higher reverse leakage current. This current, which flows through the diode when reverse biased, is typically much greater in Schottky diodes than in conventional PN junction diodes. This is because the Schottky barrier, formed between the metal and semiconductor, is less effective in preventing reverse current flow compared to the depletion region in a PN junction. The higher reverse leakage current can be problematic in applications where low leakage currents are critical, such as in analog circuits and high-impedance circuits.
Lower Reverse Breakdown Voltage
Schottky diodes generally have lower reverse breakdown voltage compared to conventional PN junction diodes. This means that they are more susceptible to damage when subjected to high reverse voltages. The lower breakdown voltage is attributed to the thin depletion region formed at the Schottky barrier. The thinner depletion region reduces the electric field required to cause breakdown. Consequently, Schottky diodes are less suitable for applications requiring high reverse voltage ratings.
Temperature Sensitivity
Another disadvantage of Schottky diodes is their greater temperature sensitivity. The forward voltage drop of a Schottky diode is significantly affected by temperature variations. As temperature increases, the forward voltage drop decreases. This temperature sensitivity can be a concern in applications where stable operating characteristics are required, particularly in environments with wide temperature fluctuations.
Limited Current Handling Capability
Schottky diodes typically have a lower current handling capability compared to conventional PN junction diodes. This is due to the smaller junction area and the lower doping concentration of the semiconductor material used in Schottky diodes. The limited current handling capability can be a drawback in high-power applications where significant current levels need to be handled.
Higher Cost
Generally, Schottky diodes are more expensive to manufacture than conventional PN junction diodes. This is due to the more complex fabrication processes involved in creating the Schottky barrier. The higher cost can be a significant consideration in applications where cost is a major factor.
When to Choose Conventional Diodes over Schottky Diodes
The decision of whether to use a Schottky diode or a conventional PN junction diode depends on the specific application and its requirements. If low forward voltage drop, fast switching speed, or high-frequency operation are paramount, then a Schottky diode may be the preferred choice. However, if low leakage current, high reverse breakdown voltage, or low cost are critical factors, a conventional PN junction diode may be more suitable.
Here's a summary of when to choose conventional diodes over Schottky diodes:
Conventional Diodes are Preferred in:
- Applications requiring low leakage current: Conventional diodes exhibit much lower reverse leakage current compared to Schottky diodes, making them ideal for applications where low leakage currents are crucial, such as in analog circuits and high-impedance circuits.
- High-voltage applications: Conventional diodes typically have significantly higher reverse breakdown voltages, making them more suitable for applications requiring high reverse voltage ratings.
- Cost-sensitive applications: Conventional diodes are often less expensive to manufacture than Schottky diodes, making them a more attractive choice in cost-sensitive applications.
- High-power applications: Conventional diodes can handle higher current levels compared to Schottky diodes, making them suitable for high-power applications.
Conclusion
Schottky diodes offer distinct advantages in terms of their fast switching speed and low forward voltage drop, making them suitable for a wide range of applications. However, they also exhibit certain disadvantages compared to conventional PN junction diodes, including higher reverse leakage current, lower reverse breakdown voltage, temperature sensitivity, limited current handling capability, and higher cost. The choice between Schottky diodes and conventional diodes ultimately depends on the specific requirements of the application. By understanding the advantages and disadvantages of each type of diode, engineers can make informed decisions and select the most appropriate diode for their circuits.