TABLE OF CONTENTS The insulated gate bipolar transistor (IGBT), which was introduced in early 1980s, is becoming a successful device because of its superior characteristics. IGBT is a three-terminal power semiconductor switch used to control the electrical energy. Many new applications would not be economically feasible without IGBTs. Prior to the advent of IGBT, power bipolar junction transistors (BJT) and power metal oxide field effect transistors (MOSFET) were widely used in low to medium power and high-frequency applications, where the speed of gate turn-off thyristors was not adequate. Power BJTs have good on-state characteristics but have long switching times especially at turn-off. They are current-controlled devices with small current gain because of high-level injection effects and wide base width required to prevent reach-through breakdown for high blocking voltage capability. Therefore, they require complex base drive circuits to provide the base current during on-state, which increases the power loss in the control electrode.
On the other hand power MOSFETs are voltage-controlled devices, which require very small current during switching period and hence have simple gate drive requirements. Power MOSFETs are majority carrier devices, which exhibit very high switching speeds. But the unipolar nature of the power MOSFETs causes inferior conduction characteristics as the voltage rating is increased above 200 V. Therefore their onstate resistance increases with increasing breakdown voltage. Furthermore, as the voltage...
