The design decision between IGBT and MOSFET was introduced in the 1980s when the insulated-gate bipolar transistor (IGBT) was introduced to the world. An IGBT is a cross between the bipolar and MOSFET transistors which gives it a few advantages. Not to be ignored however, are the numerous positives surround MOSFETs when designing new hardware. Whether you use IGBT or MOSFETs in your design, one thing is for sure: these two transistors dominate the power semiconductor market in numerous applications, to include uninterruptible power supplies (UPS), solar inverters, and motor drives to name a few. MOSFETs and IGBTs have very similar structures, however the main difference lies in the additional substrate layer in the IGBT.
Until IGBT was introduced, MOSFET where the only true power transistor available for hardware engineering jobs. IF you’re discussing power supply applications, MOSFET offers the best option. Other design features also make MOSFET a more popular solution when handling freewheeling currents or to stop thermal runaway, which include a body-drain diode, as well as, a positive temperature co-efficient. MOSFET devices make the logical choice when dealing with the following situations:
- Low Voltage Applications
- Long Duty Cycles
- Wide line or load variations
- High Frequency Applications
An IGBT semiconductor device combines the output characteristics of a bipolar transistor and the gate drive characteristics of a MOSFET. This makes IGBTs ideal for situations that need high input impedance and high current-carrying capabilities. IGBTs are better suited to scale in current handling capability at higher voltage levels than MOSFETs. Thus, if you are trying to break down voltages over 1000 V, the IGBT should be the best choice. The following conditions would warrant using an IGBT in your design:
- High Voltage Applications
- Low Duty Cycle
- Low Frequency
- Narrow or small line or load variations
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Deciding on which device to use boils down to understanding the performance of each device. In the hardware engineering world, there is a prevailing industry perception that MOSFETs are more mature because they have been around longer. Some engineers might even believe that IGBTs, because they are newer, will eventually replace MOSFETs in many applications. MOSFET performance, however, has continued to evolve, and thus, remains a dynamic product for certain types of low voltage, high frequency applications.
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