Monolithic Comparator and Sawtooth Generator of AlGaN/GaN MIS-HEMTs With Threshold Voltage Modulation for High-Temperature Applications

This article demonstrates the integrated comparators, hysteresis comparators, and sawtooth generators based on aluminum–gallium–nitride/gallium–nitride (AlGaN/GaN) metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). The integrated circuits (ICs) exhibit thermal stability from 25 °C to 250 °C in both static and transient performances. The threshold voltage ( ${V}{_{\text {th}}}$ ) in depletion (D)-mode MIS-HEMT is modulated from −8.9 to −2.4 V to optimize the performance of integrated comparator circuits. The comparator can realize a large and stable comparison range of 3–9 V and a high voltage swing of 9.1 V, while the hysteresis comparator exhibits a good noise-immunity ability and stable hysteresis output. The sawtooth generator with the hysteresis comparator features a high amplitude (6.1 V) sawtooth signal at 500 kHz to realize a compact structure applicable to the high-voltage mixed-signal circuits. These results show the feasibility of MIS-HEMT monolithic comparator circuits in conversion systems.