Resolution-Related Design Considerations for a 120-GS/s 8-bit 2:1 Analog Multiplexer in SiGe-BiCMOS Technology

This article presents a 120-GS/s 2:1 8-bit analog multiplexer (AMUX) in SiGe-Bipolar CMOS (BiCMOS) technology that exhibits the highest effective resolution reported for an AMUX in any kind of semiconductor technology. This article presents the design considerations that have led to this high resolution. In particular, it contains a discussion on the choice of an AMUX circuit concept to support high linearity. A frequency-domain explanatory model for the signal contribution to the effective number of bits (ENoB) in the presence of mismatch errors is presented and applied to the analysis of timing and signal gain mismatch in the AMUX setup. Typical ENoB versus frequency characteristics were identified and utilized to speed up ENoB simulations and to develop calibration procedures for the different mismatch types in the AMUX setup. The results of the analysis and the performance of the AMUX in the calibrated setup were proven by measurement results.