IIP3 estimation from the gain compression curve

Abstract

Classical analysis of transistor amplifier performance shows 9.6 dB as the difference between the input-referred third-order intercept point (IIP3) and 1-dB gain compression point. An analysis of amplifier gain compression shows that this is not the case, that at least fifth-order harmonics play a role in the gain compression curve and that the classical analysis is incorrect for submicrometer RF transistor amplifiers. Another approach is presented that estimates the values of IIP3 from a single-tone RF power gain data. This approach is successfully applied to simulations of a common-source amplifier and a differential amplifier with resistive load. Measurements of commercial amplifiers show that IIP3 can be estimated from their gain compression curves. This modeling approach of determining IIP3 from gain compression curves can simplify test protocol, shorten test time, and lower cost of integrated-circuit production test.