What is Small Signal Gain?

Small Signal Gain is the gain/amplification provided by an amplifier in the linear region. In the input power vs output power graph for an RF amplifier, we observe that for a specific frequency range the output power of the amplifier is proportional to the input power (initially), and we get a linear relationship (straight line). Small signal gain is the gain in this linear region. As input power increases, the amplifier approaches saturation i.e., the linear relation between input and output power breaks. This point is called the 1 dB compression point (P1dB) and small signal gain can be calculated only up to this point.

Small signal gain is relevant in scenarios where the RF amplifier is to be used at a lower power which falls in the linear region.