A gallium nitride-based operational amplifier for high temperature applications

GaN devices show improved performance in high-temperature analog and power electronic applications. However, a high-temperature all-GaN chip is challenging because of the limited availability of all-GaN system components that can operate at extreme temperatures. This paper presents the design and calibrated simulations of an operational amplifier comprised entirely of enhancement-mode and depletion-mode GaN High Electron Mobility Transistors (HEMTs) for high-temperatures up to 500°C. At room temperature, it shows a DC gain of 88 dB, a unity gain frequency of 75 MHz, a common-mode rejection ratio of 109 dB, a slew rate of 119.2 V/µs, a 0.1% settling time of 25 ns, and an input offset of -33.4 µV. At 500°C, the OpAmp maintains a DC gain of 61 dB, a unity gain frequency of 8.4 MHz, a common-mode rejection ratio of 101 dB, a slew rate of 17.5 V/µs, a 0.1% settling time of 182 ns and an input offset of -532 µV. The change of the OpAmp parameters with the electron mobility and threshold voltage of the HEMT is analyzed. Lastly, performance comparison is presented with state-of-the-art OpAmp designs based on Si, SiC, and GaN at both room and high temperatures. The authors envision that this work will contribute to establishing the wideband GaN as a predominant choice for high-temperature analog circuits and technologies.