Implication of transistor frequency dependence on intermodulation distortion

An analysis is presented for third-order and second-order nonlinear distortion as a function of frequency for a transistor biased in the common-emitter configuration. It is found that, at high frequency, it is the curvature in the loaded cutoff frequency versus collector current curve that determines the degree of intermodulation distortion. Design proposals for obtaining linear cutoff frequency curves (i.e., small third-order distortion) will be discussed.