A 4-Transistor Monolithic Solution to Highly Linear On-Chip Temperature Sensing in GaN Power Integrated Circuits

We report the monolithic realization of on-chip temperature sensing design using four transistors (4T) in gallium nitride (GaN) technology. The temperature sensor consists of a voltage reference and a logic inverter, both of which are built from enhancement-mode (E-mode) and depletion-mode (D-mode) metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). The temperature-insensitive voltage reference outputs a very stable voltage as the input of the logic inverter, which exhibits good temperature dependence in its voltage transfer characteristics. As the temperature varies from 25 to 250 °C, the output voltage of the logic inverter changes linearly. By configuring the active-load D-mode transistor as a two-dimensional electron gas (2DEG) resistor in the logic inverter, the temperature sensing solution is improved further, showing stable sensing output, higher sensitivity (31.28 mV/°C), better linearity (
$\text{R}^{{2}}$
= 0.995) and smaller error (±2.74 °C). This demonstrates a compact monolithic sensor for monitoring the on-chip temperature of GaN power integrated circuits (ICs) for protection and control.