An analytical model for the cutoff frequency and optimum noise figure of an optically controlled GaAs MESFET suitable for microwave integrated circuits and high‐frequency optical communication systems is presented. The model calculates the cutoff frequency and optimum noise figure under dark and illuminated conditions. The significant feature is that, under optically controlled operation, the cutoff frequency increases, and a drastic reduction in the optimum noise figure is obtained. Some of the predicted results under dark conditions are compared with the data available in the literature to validate our proposed model. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 279–282, 2000.