Metal-Oxide Semiconductor Field Effect
Transistor (MOSFET) and Insulated Gate Bipolar Transistor (IGBT) are the two
most popular versions among various types of switch-mode power supply (SMPS)
transistors are available today. It has been observed that MOSFETs are suitable
for low-voltage, low-current and high switching frequencies. On the other hand,
IGBTs are favorable for high-voltage, high-current and low switching
frequencies.
There may be an argument that on which device
works better in SMPS applications, the fact is this: there’s no common norm to
specify which device performs better in a particular category of circuit. It
differs from application to application, and a wide range of factors, such as
speed, size, and cost, all play a role to ordain the exact choice.
Now we are going to enlighten on the
differences between these two transistors rather than say that one is better
than the other straight away.
The MOSFET is a three-terminal fully-controlled
switch. Gate, drain and source are its three terminals. The gate/control signal
occurs between the gate and source, and its switch terminals are the drain and
source. The gate itself is made of metal. A metal oxide separates it from the
source and drain. This grants for reduced power draining and makes MOSFET an
excellent option to use as an electronic switch or common-source amplifier.
To operate satisfactorily, a positive
temperature coefficient has to be sustained by MOSFETs. As a result of this,
there’s little-to-no chance of thermal runaway. On-state losses are lower
because the transistor’s on-state-resistance, theoretically speaking, has no
limit. Also, MOSFETs can carry through fast switching applications with little turn-off
losses because they can function at high frequencies.
The IGBT is also a three terminal (gate,
collector, and emitter) full-controlled switch. Its gate/control signal takes
place between the gate and emitter, and its switch terminals are the drain and
emitter.
The IGBT puts the common gate-drive feature
found in the MOSFET with the high-current and low-saturation-voltage capability
of a bipolar transistor at the same time. It does this by utilizing an isolated
gate field effect transistor for the control input, and a bipolar power
transistor as a switch.
Turning on and off rapidly are the specific
characteristics of IGBT. Actually its pulse repetition frequency really gets
into the ultrasonic extent. This identical ability is why IGBTs are frequently
implemented in amplifiers to synthesize complex waveforms with pulse width
modulation and low-pass filters. IGBTs are also used to yield big power pulses
in fields like particle and plasma physics, and have set up a role in modern
appliances like electric cars, trains, elevators, refrigerators, vacuum cleaner
etc.
These transistors are very similar in terms of
structures. When it comes to electron current flow, a significant difference is
the addition of a p-substrate layer beneath the n-substrate layer in the IGBT.
In this extra layer, holes are injected into the highly-resistive n-layer,
generating a carrier overflow. This increment in conductivity within the
n-layer assists to lessen the total on-state voltage of the IGBT.
Unfortunately, it also obstructs reverse current flow. As a result, an extra
diode (often referred to as a “freewheeling” diode) gets placed parallel with
the IGBT to conduct the current in an inverse direction.
www.USComponent.com had been selling IGBT power transistor modules
since 2001. Thyssen Krupp, OTIS, IXYS, SONY DADC, General Motors, Hongkong
Electric Holdings Limited, Singapore Mass Rapid Transit Trains LTD,
Verkehrsbetriebe Zurich, Czech Airlines, Molex, Cisco, Omron, Good Year Tires,
Thai Airasia, Boeing, Xilinx, LEAR SIEGLER, and General Electric.
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