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Power MOSFET Basics Guide

This document discusses power MOSFET basics, including: - Power MOSFETs employ similar semiconductor processing as VLSI circuits but with different device geometry, voltages, and currents. - Power MOSFETs were developed partly due to limitations of bipolar power junction transistors (BJTs), which previously dominated power electronics applications. - Unlike current-controlled BJTs, power MOSFETs are voltage-controlled devices requiring less drive current and allowing for faster switching.

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230 views2 pages

Power MOSFET Basics Guide

This document discusses power MOSFET basics, including: - Power MOSFETs employ similar semiconductor processing as VLSI circuits but with different device geometry, voltages, and currents. - Power MOSFETs were developed partly due to limitations of bipolar power junction transistors (BJTs), which previously dominated power electronics applications. - Unlike current-controlled BJTs, power MOSFETs are voltage-controlled devices requiring less drive current and allowing for faster switching.

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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Power MOSFET Basics

By Vrej Barkhordarian, International Rectifier, El Segundo, Ca.

Breakdown Voltage......................................... 5

On-resistance.................................................. 6

Transconductance............................................ 6

Threshold Voltage........................................... 7

Diode Forward Voltage.................................. 7

Power Dissipation........................................... 7

Dynamic Characteristics................................ 8

Gate Charge.................................................... 10

dV/dt Capability............................................... 11

www.irf.com
Power MOSFET Basics
Vrej Barkhordarian, International Rectifier, El Segundo, Ca.

Discrete power MOSFETs


Source Field Gate Gate Drain
employ semiconductor Contact Oxide Oxide Metallization Contact
processing techniques that are
similar to those of today's VLSI
circuits, although the device
geometry, voltage and current
levels are significantly different n* Source
n* Drain
from the design used in VLSI tox
devices. The metal oxide
semiconductor field effect p-Substrate
transistor (MOSFET) is based
on the original field-effect Channel l
transistor introduced in the
70s. Figure 1 shows the
device schematic, transfer (a)
characteristics and device
symbol for a MOSFET. The ID
invention of the power
MOSFET was partly driven by
the limitations of bipolar power
junction transistors (BJTs)
which, until recently, was the
device of choice in power
electronics applications.
0
Although it is not possible to 0 VT VGS
define absolutely the operating (b)
boundaries of a power device,
we will loosely refer to the ID
power device as any device
that can switch at least 1A. D
The bipolar power transistor is
SB
a current controlled device. A (Channel or Substrate)
large base drive current as
G
high as one-fifth of the
collector current is required to S
keep the device in the ON
(c)
state.
Figure 1. Power MOSFET (a) Schematic, (b) Transfer Characteristics, (c)
Also, higher reverse base drive Device Symbol.
currents are required to obtain
fast turn-off. Despite the very advanced state of manufacturability and lower costs of BJTs, these
limitations have made the base drive circuit design more complicated and hence more expensive than the
power MOSFET.

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