IGBT(Insulated Gate Bipolar Transistor), It is composed of BJT(bipolar triode) and MOS(insulated gate type field effect tube), which has the advantages of high input impedance of MOSFET and low on-voltage drop of GTR.
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The switching function of IGBT is to form a channel by adding a forward gate voltage to provide a base current to the PNP(originally NPN) transistor, so that the IGBT can be switched on.
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Conversely, the reverse gate voltage is added to eliminate the channel, cut off the base current, and make the IGBT off. The driving method of IGBT is basically the same as that of MOSFET, which only needs to control the input pole N-channel MOSFET, so it has high input impedance characteristics.
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When the channel of the MOSFET is formed, the hole (few moles) from the P base is injected into the N-layer, and the N-layer is modulated for conductance, and the resistance of the N-layer is reduced, so that the IGBT also has a low on-state voltage when the voltage is high.