The final factor for determining the device's thermal capabilities within a system is the materials used for the thermal dissipation path. This path consists of the thermal interface material and the heatsink. The thermal resistive properties of these materials will have a direct result on the maximum output power the amplifier can drive without shutting down.

An easy way to determine what the maximum thermal resistance allowed from θ_CH and θ_HA is by looking at Equation 1 and Equation 2. Merging both equations gives the following:

Simplifying it further by having θ_CA = θ_CH + θ_HA gives the following equation:

Using this formula in an example where the total output power desired is 80W into 4Ω loads with an ambient temperature set at 75°C. At 80W output power, the power dissipation will be approximately 13.6W. Using θ_JC = 0.6 °C/W and deciding that the junction temperature should never rise above 130°C , θ_CA can be found by:

Thus, the total thermal resistance of the thermal solution cannot be higher than 3.44°C/W.