Distortion in broad-band gallium arsenide MESFET control and switch circuits

The author analyzes the nonlinear mechanisms of the MESFET in its passive control mode of operation and equations are developed that allow designers to predict second- and third-order harmonic and intermodulation products in the conducting state MESFET. The analytic expressions are verified by experimental data. The discussion is based on a lumped element equivalent circuit model and is limited to applications where the MESFET is operating in its conducting state. In switch circuits, the analysis indicates that distortion may be reduced by the use of MESFETs with pinchoff voltages in the 2-3-V range and with large open channel current capacities. In attenuators, the analysis shows extreme variations in the level of distortion over a relatively narrow range of attenuation levels. Distortion in the case of the reflective attenuator may be reduced by the use of MESFETs with small open channel current capabilities