High temperature performance of a SiC MESFET based oscillator

A hybrid, UHF-Band differential oscillator based on 10 W SiC RF Power Metal Semiconductor Field Effect Transistor (MESFET) has been designed, fabricated and characterized through 475 °C. The circuit is fabricated on an alumina substrate with thin film spiral inductors, chip capacitors, chip resistors, and wire bonds for all crossovers and interconnects. The oscillator delivers 15.7 dBm at 515 MHz into a 50 Ω load at 125 °C with a DC to RF conversion efficiency of 2.8 %. After tuning the load impedance, the oscillator delivers 18.8 dBm at 610 MHz at 200 °C with a DC to RF conversion efficiency of 5.8 %. Finally, by tuning the load and bias conditions, the oscillator delivers 4.9 dBm at 453 MHz at 475 °C.