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What are diodes? – Properties and Characteristics

What are diodes? – Properties and Characteristics

The fundamentals of diodes, also known as the most fundamental silicon semiconductor device, and the various types of diodes, which are referred to as silicon power devices in this context, are first discussed.

Types of Si Diodes When thinking about the various kinds of Si diodes, there probably are a few different ways to classify them, depending on the primary object. Diodes have been grouped here primarily according to their anticipated applications, such as power conversion.

We have divided diodes into rectifying diodes, Zener diodes, and radio frequency diodes as our general framework. Diodes for general-use rectification, devices for high-speed rectification assuming switching, fast-recovery type diodes for applications in ultra-high speed rectification, and Schottky barrier diodes with fast operation and low VF are further subdivided among these. Following, each of these will be discussed individually.

Si_1-1_catg These classifications have been adopted, but in all cases, the anode and cathode are the primary components of these devices, and the parameters indicating their essential features and functions are virtually identical. If the question “then how are they different?” arises, “Different electrical characteristics are optimized according to the application” is probably a good way to sum up the situation.

The static and dynamic electrical characteristics of diodes will be checked to make sure everything is right. In the event that you look at the graph underneath, a nitty gritty clarification ought not be important, however coming up next are watchwords that are expected to make sense of the qualities of diodes.

The forward voltage VF and forward current IF, as well as the reverse voltage and current VR and IR, are diodes’ fundamental static characteristics.

The usable area of rectifying diodes is depicted in the diagram on the right by the orange dashed line that surrounds it. In particular, this refers to the region that falls within the allowable IF range and the reverse breakdown voltage range.

Although Zener diodes are not the subject of this chapter, it is important to note that the area enclosed by the green dashed line is the usable area. This area cannot be used by other diodes, and device failure may occur if the IR is allowed to enter unrestricted.

Electrical Characteristics of Diodes

We will check the diode’s static and dynamic properties to be certain. In the event that you look at the graph underneath, a nitty gritty clarification ought not be important, however coming up next are watchwords that are expected to make sense of the qualities of diodes.

The forward voltage VF and forward current IF, as well as the reverse voltage and current VR and IR, are diodes’ fundamental static characteristics.

The usable area of rectifying diodes is depicted in the diagram on the right by the orange dashed line that surrounds it. In particular, this refers to the region that falls within the allowable IF range and the reverse breakdown voltage range.

Although Zener diodes are not the subject of this chapter, it is important to note that the area enclosed by the green dashed line is the usable area. This area cannot be used by other diodes, and device failure may occur if the IR is allowed to enter unrestricted.

The reverse recovery time trr and the static capacitance Ct are diodes’ primary dynamic characteristics.

The time at which a voltage is applied in the forward direction and a forward current IF is flowing is referred to as trr. At this point, the voltage is applied in the opposite direction, and the reverse current IR returns to the steady state (essentially zero). When the device moves from the ON state, where an IF is flowing, to the OFF state, as depicted in the diagram to the right, the ideal scenario would be for the IF to immediately drop to zero. However, in reality, zero has been reached, and a momentary flow of a reverse current known as IR returns to zero in time trr. The device’s characteristics improve with shorter trr.

The diode’s own capacitance, the capacitance Ct, functions similarly to a capacitor. When a diode is turned on and off, as shown in the diagram to the right, if Ct is high, the so-called rounding of the waveform gets worse. In some cases, time constants may cause the device to start turning off before an applied voltage reaches its full level. Diodes with a low Ct are ideal for a high-speed switching circuit.

Si_2-1_catg and Si_2-2_catg are the main maximum ratings and electrical characteristics that we discuss in this section.

Maximum ratings indicate the temperature as well as the continuous and instantaneous applied voltages and currents.
For the definition of “instantaneous,” either the data sheet’s description should be consulted, or the manufacturer should be consulted if there is no clear description.

Since this is the beginning of a new chapter, a lot of the above has been about fundamentals, which are important to know when thinking about diode characteristics and applications. These parameters must be examined when selecting actual diodes.

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