![]() Schottky diodes, therefore, are used where recovery time at higher frequencies matter. Additionally, with a metal-semiconductor junction, modulation and switching can be much faster.) One of the results of the metal-semiconductor junction is that the Schottky diode has a much quicker recovery time coming out of a reverse bias state. (One of the main differences is that the metal semiconductor current will be higher at the same voltage bias than a diode with a PN junction. A metal-semiconductor junction has metal in contact with the semiconductor material. Schottky diodes have a semiconductor metal junction whereas a standard silicon diode has a semiconductor junction. Zener diode shunt regulator),Īnother type of diode is the Schottky diode. Zeners are useful for protection against biasing a circuit over its rated voltage (e.g., in a crowbar circuit), regulating voltage in a circuit (a.k.a. Zener diodes are often used for circuit protection. Many diodes can withstand very large voltages before reaching breakdown. The diode’s datasheet will show the maximum ratings, including the peak level of reverse-bias voltage that the diode can withstand. However, it is possible to break any diode. When a diode is reverse-biased to the breakdown voltage, current flows in the wrong direction but the diode is not broken it’s just not working as a one-way device anymore. (Source: Infineon datasheet for IDFW40E65D1E) Figure 2: The I-V curve from a datasheet for a general-purpose switching diode that shows the diode’s typical forward current as a function of forward voltage. ![]() Thus, the I-V characteristics of Zener and avalanche diodes are meant to be used past the breakdown voltage. Zener and avalanche diodes are different from regular diodes in that regular diodes are not designed to operate in reverse-bias mode. Speaking in terms of material science, avalanche concerns the reaction of electrons to the strength of the electric field at the PN junction of the semiconductor. Avalanche is more commonly known as a catastrophic phenomenon. A diode reaches avalanche breakdown when the reverse-bias voltage exceeds the breakdown voltage. A high voltage Zener diode, also known as an avalanche diode, is meant to operate beyond the breakdown voltage. Some diodes, called Zener diodes, are specially designed with a low breakdown voltage that can be safely exceeded without damaging it. If you reverse-biased a diode past its breakdown voltage, the diode will conduct current in the wrong direction. From the IV curve, you can tell that a real diode is non-linear. An ideal diode would not conduct any current if reverse-biased (experiencing negative voltage), but would conduct current fully (as if it were just a wire) if we were to apply a positive voltage across the diode. The Current-Voltage curve of a diode (Figure 2) shows the response of the diode as a function of current versus voltage. The electrical symbol for the diode has a corresponding line that also indicates the anode and thus the direction of current flow during forward voltage operation. Figure 1: A diode has polarity indicated as a band on the cathode (-) side. The band also corresponds to the symbol of the diode, indicating current flow. An actual diode, shown to the left in Figure 1, is marked by a band on the cathode side. ![]() Current flows in one direction from the positive terminal (called the anode) to the negative terminal (called the cathode). ![]() The symbol for a diode (to the right in Figure 1) looks something like an arrow pointing in the direction of the forward current. A diode is a passive component made with semiconductor materials (a chip) that conducts current flowing in one direction but does not conduct current flowing in the opposite direction. ![]()
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