Chapter 4 - The power MOSFET

Abstract

This chapter provides an overview of power MOSFET (metal oxide semiconductor field effect transistor) semiconductor switching devices. It focuses on the terminal i–v switching characteristics of the available device, turn-on, and turn-off switching characteristics, PSPICE modeling and its current, voltage, and switching limits. Because of the functional importance, drive complexity, fragility, cost, power electronic design engineer must be equipped with the thorough understanding of the device operation, limitation, drawbacks, and related reliability and efficiency issues. The improvement of semiconductor processing technology along with manufacturing and packaging techniques has allowed power semiconductor development for high voltage and high current ratings and fast turn-on and turn-off characteristics. Efficiency is considered as an important figure of merit and has significant implications on the overall performance of the system. Low efficient power systems means large amounts of power being dissipated in a form of heat. Most of the MOSFET devices used in power electronics applications are of the n-channel. Since the MOSFET is a majority carrier transport device, it is inherently capable of a high frequency operation. But still the MOSFET has two limitations: high input gate capacitances and transient/delay due to carrier transport through the drift region. The frequency response of the MOSFET circuit is limited by the charging and discharging times of Cin. Miller effect is inherent in any feedback transistor circuit with resistive load that exhibits a feedback capacitance from the input and output.