Issue link: https://resources.mouser.com/i/1525523
| 24 Contrary to a pure power MOSFET, the on-state voltage drop of an IGBT does not fall below the threshold of a diode. Selecting the right component is not just a matter of choosing the right figures from a datasheet because the parameters change during operation. Both the R DS(ON) of the MOSFET and the on-state voltage drop of the IGBT are affected by both temperature and current, and both types of devices are susceptible to heating during operation. The MOSFET's voltage drop is proportional to the current, and its R DS(ON) increases with temperature. The voltage drop in an IGBT is similar to that of a diode, increasing with the log of the current and remaining relatively constant with temperature. The Wide Bandgap Revolution Until recently, silicon MOSFETs and IGBTs were the components of choice to power electric motors. Many applications remain perfectly acceptable options, but now further choices are available due to the commercialization of wide bandgap technologies. Over the last decade, gallium nitride (GaN) and silicon carbide (SiC) semiconductors have come onto the market, offering traits better than silicon transistors in almost all cases. The bandgap is the energy required for electrons and holes to transition from the valence band to the conduction band. While silicon has a bandgap of 1.12eV, SiC and GaN have band gaps of 3.26eV and 3.39eV, respectively. The breakdown fields of the three materials tell a similar story. SiC is 3.5MV/cm, GaN is 3.3MV/cm, and silicon is 0.3MV/cm. These figures mean that GaN and SiC are over ten times more capable of maintaining higher voltages. In practical terms, the two wide bandgap materials can switch faster and handle higher voltages for longer, making them more efficient. They can also withstand higher operating temperatures than silicon—around 600°C for SiC and 300°C for GaN, compared to only 200°C for silicon devices. Those benefits alone mean that wide bandgap designs can provide smaller and lighter solutions, better performance, and easier thermal management. Although the bandgap figures look similar for GaN and SiC, their electron mobility figures are very different, and those play a large part in dictating how the new materials are used for power-handling applications. Electron mobility measures how fast an electron can travel through a conductor or semiconductor material when pulled by an electrical field. GaN is fastest with an electron mobility of 2,000cm 2 /Vs, silicon comes next with 1,400cm 2 /Vs, and SiC offers 650cm 2 /Vs. Those better specifications mean that GaN can switch rapidly, ten times faster than silicon MOSFETs. High Power IMS 3 Evaluation Platform mouser.com/gan-systems-ims-3-evaluation-platform