Hello,
The Saturation power (Psat) is the power level achieved, even changing the input power does not produce any change in the output power level.
The dissipation power is is the maximum allowed continuous power dissipation for a device with a mounting base at 25 C. The power dissipation is calculated as that which would take the device to the maximum allowed junction temperature while keeping the mounting base at 25 C.
The maximum rating for power dissipation (PD) is closely associated with thermal resistance (θJC). Actually maximum PD is in reality a fictitious number a kind of figure of merit because it is based on the assumption that case temperature is maintained at 25°C.
Hope this helps.
