Each GaAs FET or bipolar transistor has its own unique ability to withstand excessive input power levels. This capability is related to device geometry, metal thickness, fabrication techniques and materials. Since the input circuit of most transistor amplifiers is tuned for maximum power transfer, the power withstanding capacity of an amplifier is practically the same as that of the input transistor or transistors.

If excessive power is applied to a transistor amplifier, the fast measurable affect is almost always an increase in noise figure. A somewhat higher power will further degrade noise figure and decrease the gain of the amplifier. If the input power level is even higher, the input transistor will ultimately fail.