On the other hand, if IGBT’s Gate terminal is zero voltage or slightly negative, it shuts OFF the circuit application. If a positive input voltage goes across the Gate, the Emitter keeps the drive circuit ON. The IGBT working principle is ON or OFF by either activating or deactivating its Gate terminal. The IGBT is preferable over the thyristor because of the fast toggling over the thyristor’s wait for zero crossings. But, the thyristor actions and functionality are suppressible, meaning that only transistor action is permissible in the IGBTs entire device operation range. NOTE: IGBT’s structure is topologically similar to a thyristor in terms of the “MOS ” gate. Similarly, the junction between the N- Region and the Body Region is junction J1. Note that the junctions between the Collector region (or Injection Region) and the N-Drift Region are J2. Inside the Body Region, there are (n+) layers. On top of the Drift Region is the Body Region, which consists of (p) substrate. The thickness of the Drift Region determines the voltage blocking capability of the IGBT. The Injection Active Region injects most of the carrier (the hole current) from the (p+) into the N- layer. Right, above it is the N- Drift Region, which comprises the N- layer. The layer closest to the Collector region is the (p+) substrate, the Injection Region. The four-layer device comes about by combining PNP and NPN transistors, which make up a PNPN arrangement. Internally, the IGBT structure is a four-layer device of semiconductors. However, the metallic material on the Gate terminal has insulation of a silicon dioxide layer. Structure of IGBTĪll three terminals (Collector, Emitter, and Gate) of IGBT are attached with metal layers. The input side represents the MOSFET, while it takes the output symbol from BJT’s symbol.Īs expected, the conduction terminals are the Collector and Emitter. The symbol also has three terminals – the Collector, Emitter, and Gate. Since IGBT combines BJT and MOSFET, its symbols follow the same principle as below. IGBT provides fast switching at high efficiency. Therefore, an IGBT is a three-terminal device used as a switching device and applicable in amplifying signals. The IGBT combines both the BJT and MOSFET, whereby it takes the best of both transistors.
While BJTs prefer low on-state drops, MOSFETs are best for their high I/P impedance, low switching loss, and lack of secondary breakdown. The commonly used transistors are BJT (Bipolar Junction Transistor), MOSFETs, and IGBT.īoth BJTs and MOSFETs have their preferences, as well as advantages over the other.
There are different types of transistors based on other usefulness or specific applicability. It acts as a switch to control lighting circuits and can amplify signals. A transistor is a small electronic component with two main functions.
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