p-GaN HEMT current reference and current mirror for high temperature application

This paper demonstrates a monolithically integrated current reference and current mirror based on p-GaN gate HEMT technology, designed for high-temperature applications. The p-GaN current reference is composed of one D-mode and two E-mode devices. The generated reference current is independent of supply voltage since the proposed circuit incorporates a bias circuit capable of providing a supply-voltage-insensitive bias voltage. Moreover, under the zero-temperature coefficient (ZTC) bias voltage condition, the variation in the generated reference current at 200 °C is reduced by 15.4%, compared to a conventional p-GaN current reference with a bias voltage of 5 V. Experimental results indicate that the generated reference current slightly reduced from 2.53 to 1.70 mA over a broad temperature range of 25−200 °C. In addition, a current mirror circuit based on p-GaN HEMT technology was designed to imitate a reference current. The influence of temperature on the output current of the current mirror is mitigated, which could be realised by biasing the gate-to-source voltage at the zero-temperature coefficient voltage. This design sustains the current mirror mismatch error with small variation across a temperature range from room temperature to 200 °C. These results indicate that the GaN current reference and current mirror under zero-temperature coefficient bias voltage can ensure stable output current across different temperatures, facilitating the application of fully GaN integrated circuits in high-temperature environments.