All linear amplifier systems, when given a sufficiently strong input signal, will reach a point where the system departs from a linear relationship between input and output. At this point the system is said to be going into compression or beginning to saturate. Beyond this point, the linear relationship between input and output is no longer valid and the amplifier is no longer considered to be linear. An internationally recognised figure of merit, used for defining the extent of linearity of an amplifier, is the 1dB compression point. This is the point of –1dB departure from linearity. The output power of an amplifier cannot increase indefinitely and when an increase in input power generates no discernible increase in output power, the amplifier is said to be saturated, and by definition the output is not proportional to the input signal. This point is often referred to as Psat on a datasheet or sometimes P3dB. Generally, saturated power is of importance when considering the pulsed power requirements in something like automotive testing while linear power is of importance when considering the AM (amplitude modulation) waveform used in commercial EMC testing.