IP3 is related to amplifier linearity. Which statement is most accurate?

• A. The input second-order intercept point; it indicates how well an amplifier handles even-order distortion.
• B. IP3 measures the DC bias stability of the amplifier.
• C. IP3 refers to third-order intermodulation distortion and linearity in an amplifier; higher IP3 means better linearity.
• D. IP3 is a measure of the second-order distortion.

Answer: (C)

IP3 is about how an amplifier handles multiple signals and how linear it stays when those signals mingle. In a two-tone test, the amplifier not only passes the two fundamental tones but also creates intermodulation products, especially at third-order frequencies like 2f1−f2 and 2f2−f1. The output power of these third-order products grows faster with input than the fundamental signals, so if you extrapolate the lines for fundamental and third-order products, they would cross at a point called the third-order intercept point. A higher IP3 means those distortion products stay smaller relative to the wanted signals until higher input levels, i.e., better linearity. The other statements talk about second-order intercepts, DC bias stability, or second-order distortion, which are not what IP3 measures.