The operation of dual-gate GaAs MESFET\´s in gigabit-per-second switching applications for high-speed fiber-optic systems is investigated, and a full nonlinear modeling procedure is presented for general switching simulations. The model is characterized via a new and efficient technique which only requires two-port

-parameter measurements to determine the nonlinear element variations. Circuit simulations implemented on program SPICE 2 have been applied to evaluate the transient switching response of dual-gate MESFET\´s in several circuits involving 1-Gbit/s pulse conversion and synchronization, pulse-width reduction and 2-Gbit/s multiplexing, and results show good agreement between predicted and experimental switching waveforms.