Characterization and design of GaAs SCFL latched comparators basedon improved linearized models

摘要

This brief presents characterization and design considerations of high-speed and high-precision GaAs latched comparators consisting of source coupled FET logic (SCFL) flip flops. In order to characterize the comparators, linearized equivalent circuit models are improved for the SCFL flip flops. Based on the models, critical design parameters such as recovery time, regeneration time and input voltage sensitivity are determined for the comparators. Circuit configurations for increasing circuit speed and accuracy are characterized and compared. One comparator is optimized and implemented in a 0.5 μm GaAs E/D HEMT technology. Measurement results demonstrate the implemented comparator achieves an average voltage sensitivity of 11.5 mV at low frequencies and an optimal voltage sensitivity of 10.0 mV at an input signal frequency of 2 GHz and a clock frequency of 4 GHz. Predicted voltage sensitivities are also verified to be in good agreement with the measured results