High-frequency nonlinearity analysis of common-emitter and differential-pair transconductance stages

Equations describing the high-frequency nonlinear behavior of common-emitter and differential-pair transconductance stages are derived. The equations show that transconductance stages using inductive degeneration are more linear than those using capacitive or resistive degeneration, and that the common-emitter transconductance stages are more linear than the differential-pair transconductance stages with the same bias current and transconductance. The nonlinearity equations can also be used to explain the class AB behavior of the common-emitter transconductance stage with inductive degeneration.