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Component Specifications

Average Power (Thermal)

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The continuous RF power handling capability of a component determined by its thermal dissipation capacity. The average thermal power rating specifies the maximum CW power level at which the component can operate without exceeding its maximum temperature rating, accounting for ambient temperature, mounting conditions, and cooling method.
Category: Component Specifications
Limit: Junction/body temperature
Derate: With ambient temp and altitude

Comparison

ParameterTypicalHigh-PerfUnitNotes
FrequencyStandardExtendedGHzBand-dependent
PerformanceNominalOptimizeddBApplication-specific
LinearityModerateHighdBcSystem requirement
IntegrationDiscreteMonolithic—Cost vs performance
CostLowPremium$Volume-dependent

Understanding Average Power (Thermal)

P_max = (T_junction_max - T_ambient) / R_theta_JA. Derating: P_derated = P_rated x (T_max_rated - T_ambient_actual) / (T_max_rated - T_ambient_rated). Example: 100W termination rated at 25C ambient, max 150C: At 85C ambient, P_derated = 100 x (150-85)/(150-25) = 52W.
Common Questions

Frequently Asked Questions

Why must average power be derated at high ambient temperature?

The component junction temperature must stay below its maximum rating. If ambient temperature rises, the temperature budget for RF heating decreases proportionally. A termination rated at 100W at 25C can only handle 52W at 85C because it has less thermal headroom.

How does heatsinking affect average power rating?

The thermal resistance R_theta from junction to ambient determines the power rating. A proper heatsink reduces R_theta from perhaps 5 deg C/W (free air) to 1 deg C/W (forced-air heatsink), increasing the power rating by 5x. The component datasheet specifies the rating for a given mounting condition.

What is the difference between average and peak thermal power?

Average thermal power is limited by steady-state heat dissipation (seconds to minutes time constant). Peak thermal power can temporarily exceed the average rating because thermal mass absorbs the heat pulse before the junction reaches maximum temperature. Pulse duration and duty cycle determine the allowable peak power.

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