Four characteristics of Schottky diode — SUNMATE

Schottky diode is an important device in the production of electronic products. Because it plays an important role in protecting the circuit, it is particularly indispensable. We all know that when choosing Schottky diode, it mainly depends on its forward conduction voltage drop, reverse withstand voltage, reverse leakage current, etc.

However, we seldom know the relationship under different currents, reverse voltages and ambient temperatures. Knowing these relationships in circuit design is very important for selecting appropriate Schottky diodes, especially in power circuits. Knowing its characteristics makes it easier for us to use it. Now let's take you to understand the characteristics of Schottky diodes.

1. Relationship between forward conduction voltage drop and conduction current

When a forward bias voltage is applied to both ends of the Schottky diode, its internal electric field region becomes narrower, and a large forward diffusion current can pass through the PN junction.

Only when the forward voltage reaches a certain value (this value is called "threshold voltage", germanium tube is about 0.2V, silicon tube is about 0.6V), the Schottky diode can be truly turned on. If the price allows, try to choose Schott diodes with small conduction voltage drop and rated working current twice as high as the actual current.

2. Relationship between forward conduction voltage drop and ambient temperature

In the process of developing products, the impact of high and low temperature environment on electronic components is the biggest obstacle to the stable work of products. The influence of ambient temperature on most electronic components is undoubtedly huge, and Schottky diodes are no exception. In high and low temperature environments, the conduction voltage drop of Schottky diodes is inversely proportional to the ambient temperature.

Although the conduction voltage drop is the largest when the ambient temperature is -45 ℃, it does not affect the stability of the Schottky diode. However, when the ambient temperature is 75 ℃, the housing temperature has exceeded 125 ℃ given in the data book, so the diode must be derated at 75 ℃. This is also one of the factors why switching power supply needs to be derated at a certain high temperature point.

3. Relationship between Schottky diode leakage current and reverse voltage

When reverse voltage is applied to both ends of Schottky diode, its internal electric field area becomes wider, and less drift current passes through PN junction, forming what we call leakage current.

Leakage current is also an important parameter to evaluate the performance of Schottky diodes. Large leakage current of Schottky diodes not only increases its own temperature, but also affects its efficiency for power circuits. The leakage current under different reverse voltages is different. The relationship shows that the larger the reverse voltage is, the greater the leakage current is, and the leakage current of Schottky diodes can be ignored at room temperature.

4. Relationship between Schottky diode leakage current and ambient temperature

In fact, the biggest influence on the leakage current of Schottky diodes is the ambient temperature, which is the relationship curve tested under the rated back voltage, from which we can see that the higher the temperature is, the greater the leakage current is.

It rises in a straight line after 75 ℃, and the leakage current at this point is one of the two factors that cause the Schottky diode housing to reach 125 ℃ under the rated current. Only by derating the reverse voltage and forward conduction current can the operating temperature of Schottky diode be reduced.