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25 | The very low gate capacitance of GaN designs also leads to lower switching losses. A great example of how GaN transistors can change power designs can be seen in USB chargers for cell phones, which have shrunk in size, even as their power-handling capabilities have grown from around 11W to 70W. As such, GaN provides an ideal solution for motor applications up to 650V and 20kW that need the highest efficiency possible. On the other hand, SiC switches a lot slower than GaN while still being faster than silicon solutions. The wide bandgap material offers additional power delivery benefits, such as high voltage and current handling, high thermal conductivity, and robustness. The higher switching frequencies of SiC make it preferable for designs that require high efficiency and accuracy up to around 1,200V and 200kW. Of course, there are trade- offs required to get that better performance. Wide bandgap semiconductors are much harder to drive than MOSFETs and IGBTs, leading to increased design time and complexity. Additionally, one of the most significant advantages of using wide bandgap materials is that the faster switching allows smaller filter components to be used. However, motor applications don't use filters extensively, as the motor windings can be used to smooth the PWM signal. Even the moderate switching speeds provided by MOSFETs and IGBTs offer almost perfect waveforms. SiC and GaN transistors can also suffer reverse recovery losses in operation. Based on initial cost, IGBTs and MOSFETs are less expensive than SiC and GaN transistors, which means they may be a better option for many cost- sensitive applications. However, although SiC and GaN transistors are more expensive than their silicon counterparts, their higher efficiency in the field may make them the cheaper solution over the entire application lifecycle. All of the types of transistors we have described are perfectly acceptable choices depending on the needs of the application. In fact, as shown in Figure 4, there are significant overlaps at around the 100kHz/10kW level, and all four transistor types may be viable choices. Of course, GaN and SiC transistors are still in their early stages of development, and future generations of the devices will likely improve in performance and lower in cost. That's not to say that IGBTs and MOSFETs will remain as they are now. For example, recently introduced trench IGBTs offer improved performance, reduced size, and better thermal performance. Figure 4: The approximate application areas of modern power semiconductors. (Source: Qorvo)