Effect of circuit parameters and topology on intermodulation in MESFET circuits

Third-order intermodulation intercept is a very important criterion in communication circuits and the authors present a preliminary investigation of the mechanisms responsible. It is shown that interaction of the intrinsic MESFET second-order nonlinearity with linear circuit and parasitic components can cause significant distortion. MESFET output conductance is shown to also cause an interaction effect. Hence, intercept points quite different from those predicted by standard device characterization techniques can be obtained. Some regions of enhanced performance have been identified. Circuit topology also plays a key role in determining distortion. Some experimental results are given.<>