Feasibility of picosecond electrical sampling using GaAs FET

A fully MESFET hybrid sampling system has been built and tested. The circuit includes an FET sampling gate, an FET sampling pulse generator, and an FET test step generator. These functions have been studied separately using a large-signal model and picosecond instrumentation. The parameters of each of them are optimized to obtain the best performances. Measurements with the GaAs FET sampler are performed and a time-domain resolution better than 28 ps corresponding to a bandwidth of 12 GHz is obtained. In particular, the measurements performed on the MESFET sampling system are in good agreement with those obtained on the conventional S4 reference sampling head.