Introduction to Power MOSFETs And Their Applications

Focus:

This 14-page application note explains operation of n-channel power MOSFETs particularly as relates to their use in switched-mode power supply (SMPS) circuits. It describes their basic structures, the mechanisms that govern current flow in these devices, and their switching behavior. Some comparisons are made with bipolar transistors. Steady state and transient thermal models (the latter for pulsed applications as in SMPSs) are presented. Other concepts such as threshold voltage, safe area of operation, on-resistance, and transconductance are also explained. Key equations are presented and graphs for example devices from National are used to illustrate the explanations. Article concludes with a discussion of gate drive circuits including different types of load switching waveforms and formulas for power dissipation, explanations of how the different gate drive circuits work, and some tips on selecting them.

What you’ll learn:

• How to understand the basic operation of n-channel enhancement-mode power MOSFETs and key concepts of their use in SMPSs

Notes:

Originally published as National Semiconductor Application Note 558 in 1988, republished in 2011 by Texas Instruments.

View the Source

Author & Publication:

Ralph Locher, National Semiconductor (now Texas Instruments), Vendor website, Dec 01 1988

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