The purpose of this paper is to present a technology for GaAs integrated circuits which allows stable operation in the temperature range from 20°C to 300°C. We shall show by some examples that it is possible to fabricate MESFET-based integrated circuits with small temperature dependence up to 300°C. Long term thermal stress tests demonstrate the excellent reliability of the technology. However, the need for adequate design tools will be shown as well, as more complicated circuits have an unpredictable behaviour at very high temperatures
