The junction-to-case thermal resistance of a TO-220 packaged device (which typically matters less than the case-to-ambient thermal resistance), depends on the thickness and the area of the semiconductor die inside the package, typically in a range between 0.5 °C/W and 3 °C/W (according to one textbook)[6] or 1.5 °C/W and 4 °C/W (according to another).[5]