[SOLVED] Calculating FET temperature rise

[Zak28]

I CAN calculate out power dissipation for fets by hand however I obtained ~RMS 170mW for a fet via simulation. Junction to ambient (no heatsink involved) would be ~120°C/W (sot-23 steady state) thus thermal rise for device is simply 0.17*120? In which case it would rise 20.4°C over ambient temp. Im pretty sure this is correct but Im not sure, please let me know if its proper.

Your input is greatly appreciated.

 

[FvM]

Basically correct. Besides average power, pulse power rating may need checking.