![]() ![]() On the negative side, they require a special drive circuit with very high gate current requirements that reduce efficiency.Ĭascode GaN: This approach creates a stacked die cascode by co-packaging a naturally “off” low-voltage, low R DSon silicon MOSFET placed in series with the depletion-mode GaN HEMT transistor (Figure 3). ![]() This allows precise control of on/off switching speed and can be connected in parallel to support higher current applications. The industry has developed several approaches to “normalize” GaN device drive characteristics:Įnhancement-Mode Gate Injection Transistor (GIT): Adding a p-doped gate to aGaN- GIT causes it to function as a normally-off device (Figure 2). Their high dV/dt can reduce efficiency by creating shoot-through during the “hard” switching transition. Paradoxically, the switching speed of these devices can be too fast, which can cause ringing and injection of unwanted high frequencies into the circuit they are driving. They have low gate-to-drain capacitance and start to conduct significant current at 1.6 V, so care must be taken to ensure a low impedance gate-to-source path when the device needs to be held off during high-speed switching in a rectifier function. GaN’s electrical properties differ from silicon devices. GaN’s sweet spot is applications with operating voltages between 48 V and 600 V, making it well-suited to offer more compact, cooler-running, and cost-effective alternatives to Si-based MOSFETs. ![]() These characteristics enable more efficient solutions, run cooler, are four times smaller, and cost 10%-20% less than an equivalent Si-based design (Figure 1). Higher switching frequencies allow designers to make tradeoffs between efficiency and switching speed for application-optimized designs. GaN offers low R DSon/V DSon, high electron mobility, and other characteristics that result in more efficient designs. ![]()
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