P1dB vs Psat: Understanding RF Output Power

01 / ENGINEERING REVIEW

What the two ratings describe

P1dB is the output level where gain has fallen 1 dB below its small-signal value. Psat describes saturated output under the manufacturer’s stated test conditions. These are different operating points; there is no universal conversion between them.

02 / ENGINEERING REVIEW

Keep the qualifiers attached

A typical Psat value is not a guaranteed minimum P1dB value. Check frequency, temperature, supply, drive and CW/pulse conditions. Do not infer a rating definition when the catalog says only “output power.”

03 / ENGINEERING REVIEW

Read watts and dBm correctly

Power in dBm = 10 log10(power in milliwatts). Therefore 20 dBm = 100 mW = 0.1 W, while 30 dBm = 1 W. Convert units only after identifying which power rating you are comparing.

04 / ENGINEERING REVIEW

What to request

• Minimum output across your complete band.
• The relevant compression or saturation definition.
• Performance for your waveform and linearity requirement.
• The current model-specific datasheet and revision.

For an example of a catalog entry with a P1dB rating, review HD35269 and its linked datasheet. Its rating must not be compared directly with an unrelated amplifier’s Psat headline.