Silicon Carbide (SiC) power devices are increasingly in demand for operations which require ambient temperature over 300°C. This paper presents circuit applications of normally-on SiC VFETs at temperatures exceeding 300°C. A DC-DC boost converter using a 4H-SiC VJFET and a SiC Schottky Diode was fabricated and operated up to 327°C. A power amplifier achieved a voltage gain of 3.88 at 27°C dropping to 3.16 at 327°C. This 20 % reduction is consistent with the fall in transconductance of the device.