Integrated circuit including semiconductor power device and electrically isolated thermal sensor

An integrated circuit (10) includes a thermal sensing device (20) and a power-switching device (12) such as an IGBT. The power device (12) is fabricated in a conventional manner on a semiconductor substrate, and the thermal sensing device (20) is fabricated on an electrical insulation layer (74) formed over the substrate. The thermal sensing device (20) may be provided in the form of a number of series-connected polysilicon diodes (D1-D3) positioned adjacent to the power device (12) such that the operating temperature of the thermal sensing device (20) is near that of the power device (12). In response to an input current IC, the thermal sensing device (20) produces an output voltage (VD) that is substantially linear with surface die temperature, and which reacts rapidly to changes in surface die temperature. The thermal sensing device (20) is completely electrically isolated from the power device, thereby eliminating any electrical interaction therebetween.