IGBTtransistorer

The insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device that combines the high input impedance and fast switching of a MOSFET with the high current-carrying capability and low on-state voltage drop of a bipolar transistor. It is built as a PNPN structure and is controlled by a metal-oxide-semiconductor (MOS) gate, which insulates the gate from the underlying channel.

In operation, applying a positive voltage to the gate relative to the emitter forms a conductive channel in the silicon near the gate. This enables injection of carriers from the collector into the base region, allowing current to flow from the collector to the emitter with relatively low voltage drop. When the gate drive is removed, the device stores charge and turns off more slowly than a pure MOSFET, a behavior that is managed through drive circuitry and, in many designs, by an antiparallel diode to handle reverse or inductive currents. Some IGBTs are designed to block reverse voltages as well (reverse-blocking IGBTs).

IGBTs are valued for handling high voltages and currents with a gate drive that is easier to obtain than for BJTs, while offering lower on-state losses than many MOSFETs at comparable power levels. They require isolated gate drive and proper protection against overvoltage, overcurrent, and thermal stress. Typical applications include motor drives, industrial inverters, renewable-energy converters, uninterruptible power supplies, welding equipment, and traction systems in trains and trams.

Advancements continue in reducing switching losses, improving reverse conduction options, and integrating protective features in power modules for reliable, high-performance operation in demanding environments.