Introduction to Power MOSFETs And Their Applications
by Ralph Locher, National Semiconductor (now Texas Instruments), Vendor website, Dec 01 1988
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.
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