Velleman DCA75 - Manual (Page 21)

Atlas DCA Pro User Guide December 2012 – Rev 1
Page 21
N-Ch Enhancement
mode MOSFET
Red-G Green-S Blue-D
Gate threshold
VGS(on)=3.625V
at ID=5.00mA
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 (ie. 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.