The current increases as the voltage source (V G) increase. This will allow a channel for the current to the current to flow from the collector to the emitter between the J 2 junctions. The accumulation of negative charge carriers will increase as the voltage source at the gate terminal increases. This will result in the insertion of the negative charge carriers in the p region. As the gate voltage is increased, the capacitance effect will take on the silicon dioxide layer which would cause the negative ions to accumulate on the upper layer and the positive ions to accumulate on the lower side of the silicon dioxide layer. Only a small amount of voltage is required for it to go into a conduction state. Hence, the gate terminal is in a non-conductive state. At the start, no voltage is applied to the gate terminal. The junction J 2 is reverse biased and no current will flow inside the IGBT from the collector to the emitter. Junction J 1 is forward biased due to the V CC. The collector is positive to the emitter. The voltage source (V CC) is connected across the emitter and the collector. The voltage source (V G) is connected to the gate terminal in a positive direction to the emitter and collector. This is done to ensure that the parasitic thyristor doesn’t latch-up which would cause the latching of the IGBT. The base and emitter terminals are connected through the resistor R b of the NPN transistor. The collector of Q 1 shares the same base as Q 2 and the collector of Q 2 is the same as the base of Q 1. The drift region experiences a resistance which is known as R d and the resistance offered by the p body region is known as R b. Q 1 BJT is a p-n-p transistor and Q 2 is an n-p-n BJT. In this structure, it can be observed that it is an n-channel MOSFET and has two bipolar junction transistors (BJT) which are Q 1 and Q 2. P-channel IGBT shares a similar structure to the N-channel IGBT except the doping is reversed in each layer. The P+ layer at the bottom is the drain or the collector. The n+ layer at the top of the IGBT is the source or the emitter. The other two layers are called the body region (J 2) and the drift (J 1).

The injection layer is very integral to the characteristics of the IGBT. The only difference is that the injection layer is p + and not n + substrate as in Power MOSFET. IGBT is made of silicon and is very similar in structure to Power MOSFET.

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