.SUBCKT TIP35C_TH 1 2 3 Q1 1 2 4 TIP35C * Thermal model: 1A = 1W, 1V = 1°C RthJC 4 3 1.0 ; 1°C/W junction-to-case Cth 4 3 0.01 Etemp 5 0 VALUE V(4,3)+25 ; Temperature in °C .ENDS
Then tie the temperature back to the BJT via TEMP=V(5) . This reveals that at 20A continuous, the junction hits 150°C in under 200ms – information you cannot get from a static .OP analysis. tip35c spice model