How to calculate the junction temperature when the power is dissipated in a semiconductor device

When the power is dissipated in the semiconductor device, the junction temperature rises.
The temperature rise ΔT_j is shown as follows:
ΔT_j  [deg.C]＝ R_th [deg.C /W] × P_LOSS [W]
ΔT_j: Junction temperature rise
R_th: Thermal resistance
P_LOSS: Power dissipation in the semiconductor device

Junction temperature is shown as follows:
T_j = ΔT_j + T_a
T_j: Junction temperature
T_a: Ambient temperature
＊In a bipolar transistor, T_j is used as the symbol of junction temperature.
In a MOSFET, T_ch is used as the symbol of channel temperature instead of T_j.

For calculation of junction temperature, please refer to “Thermal Design and Attachment of a Thermal Fin: Power MOSFET Application Notes”

• Thermal Design and Attachment of a Thermal Fin: Power MOSFET Application Notes (PDF:1,061KB)