A 20-GHZ 8-BIT MULTIPLEXER IC IMPLEMENTED WITH 0.5-MU-M WNX W-GATE GAAS-MESFETS/

An ultrahigh-speed 8 bit multiplexer (MUX) has been developed for futu re-generation optical-fiber communication systems having a data rate o f 20 Gb/s, This IC was fabricated using a 0.5 mu m WNx/W-gate GaAs MES FET process based on optical lithography, ion implantation, and furnac e annealing for good reproducibility and high throughput. The WNx/W bi layer gate has a low sheet resistance, improving the circuit high freq uency performance, To attain 20 GHz operation, advanced circuit techni ques for the source-coupled FET logic(SCFL) were introduced, A cross-c oupled source-follower (CCSF) was developed mainly for the highest spe ed buffers to enhance the bandwidth. The first-stage T-type hip-hop wa s designed with optimization techniques and operated up to 21.1 GHz.