Dispersion of linearity in broadband FET circuits

A novel view of dispersion of linearity in broad-band circuits is offered, whereby memory effects impart a frequency dependence to linearity of FET amplifiers. The considerable variation in intermodulation across wide bandwidths due to trapping and heating mechanisms are considered here as a dispersion of linearity that is bias dependent. This is of interest to designers because the dispersion gives intermodulation a strong dependence on center and spacing of test frequencies, which requires an interpretation of intermodulation measurements and specifications across the whole signal bandwidth. This is important for meeting legislative requirements or for designing for good spurious-free dynamic range, and for improving the performance of linearization techniques where band-limiting of optimal linear conditions may occur.