Insulated Gate Bipolar Transistor (IGBT): Understanding Its Operations and Applications
Insulated Gate Bipolar Transistor (IGBT): Understanding Its Operations and Applications
Insulated Gate Bipolar Transistor, or IGBT, is an advanced power semiconductor device that combines the features of both BJT (Bipolar Junction Transistor) and MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). This versatile component plays a crucial role in power electronics and is widely used in various applications due to its efficiency, high power handling capacity, and fast switching capabilities.
Operational Principle of IGBT
The internal circuit of an IGBT includes two BJT transistors, one MOSFET, and a JFET (Junction Field-Effect Transistor). The operation of IGBT can be visualized through the following diagram:
In this configuration, the collector of the PNP transistor is connected to the NPN transistor through a JFET. The JFET serves as a current path between the collector of the PNP transistor and the base of the NPN transistor. This setup forms a parasitic thyristor, which creates a negative feedback loop. A resistor RB is placed to short the base and emitter terminals of the NPN transistor, thereby preventing the thyristor from latching up and leading to IGBT latch-up. The JFET also allows the MOSFET to support most of the voltage, enhancing the overall performance of the IGBT.
IGBT as a Power Device
IGBT is essentially a power BJT with a base current provided by a MOSFET. This combination offers several advantages, including a voltage-controlled input and high power handling capabilities. In terms of functionality, an IGBT can be used in small signal amplifier circuits just like a BJT or MOSFET; however, it is primarily used as a switching device in power electronics applications.
The terminals of an IGBT are labeled as Collector (C), Emitter (E), and Gate (G). Activating or deactivating the Gate terminal is what turns the IGBT "ON" or "OFF," respectively. Applying a positive voltage signal between the Gate and the Emitter keeps the device in its "ON" state, while making the input gate signal zero or slightly negative will cause it to switch to the "OFF" state.
Applications and Packaging of IGBT
IGBTs can be found in a wide range of applications, thanks to their efficiency and versatility. They are particularly suited for use in switch circuits, including H-Bridges and inverters. Due to their diverse applications, IGBTs come in various packaging types, catering to different power and environmental needs.
Many modern IGBTs are available with built-in opto-isolation, which enhances safety and performance in control systems. High-power IGBTs can also be found in modular designs, often comprising multiple IGBTs running in parallel for enhanced power handling capabilities. It is essential to select the appropriate IGBT device for your specific requirements, carefully reading the manufacturer's data sheets to understand the current and voltage limits, switching speeds, power dissipation, and other critical parameters.
Read more about IGBT on Wikipedia for a detailed understanding of the device and its specifications.
References:
IGBT - Wikipedia
Francesco Bassi for suggesting this post as an answer.