Enhancement Mode Mosfets - Peak Electronics DCA75 User Manual

Atlas DCA Pro User Guide

Enhancement Mode MOSFETs

MOSFET stands for Metal Oxide Semiconductor Field Effect
Transistor. Like bipolar transistors, MOSFETs are available in
two main types, N-Channel and P-Channel. Most modern
MOSFETs are of the Enhancement Mode type, meaning that
the bias of the gate-source voltage is always positive (For N-Channel types).
The other (rarer) type of MOSFET is the Depletion Mode type which is
described in a later section.
MOSFETs of all types are sometimes known as IGFETs, meaning Insulated
Gate Field Effect Transistor. This term describes a key feature of these
devices, an insulated gate region that results in negligible gate current for both
positive and negative gate-source voltages (up to the maximum allowed values
of course, typically ±20V). IGFETs are not to be confused with IGBTs
(Insulated Gate Bipolar Transistors), these are dealt with in a later section.
The first screen to be displayed gives
information on the type of MOSFET
detected and the pinout.
Pressing scroll-off will then result in
the gate threshold of the MOSFET being
displayed.
The (on) gate threshold voltage is the gate-source voltage at which conduction
between the source and drain starts. The DCA Pro determines that drain-source
conduction has started when it reaches a current of 5.00mA, this is confirmed
on the display.
An enhancement MOSFET will always have a gate threshold voltage of greater
than 0V (i.e. always positive relative to the source pin for N channel devices).
The DCA Pro can drive the gate from 0V to 10V for enhancement mode
MOSFETs.
N-Ch Enhancement
mode MOSFET
Red-G Green-S Blue-D
Gate threshold
V GS ( on )=3.625V
at I D =5.00mA
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April 2015 – Rev 1.4