GAAS-MESFET CIRCUIT STRUCTURES BASED ON VIRTUAL GROUND CONCEPT FOR HIGH-PERFORMANCE ASICS

Two types of circuit architecture for GaAs LSI are described. The first circuit is named Stacked DCFL which has supply voltage compatibility with Si CMOS/BiCMOS and ECL operating on 3 V or 3.3 V. A divide by 128/129 prescaler IC has been developed to confirm the Stacked DCFL circuit operation. The second circuit is named SVFL which operates on single supply voltage by using Schottky FET characteristics in spite of normally-on FET logic. Both circuit architectures are based on the virtual ground concept. The transition time of 45 psec was obtained by the SVFL ring oscillator circuit fabricated with 1 mu m gate length FET process, and the transition time of DCFL using the same process was from 80 psec to 100 psec. Stacked DCFL and SVFL are candidates for an internal gate and an input/output interface circuit for GaAs ASIC, respectively.