This work presents the thermal noise analysis results ofring amplifiers in the MDAC of cyclic ADC. Ring amplifier is an alternativeclosed-loop structure for residual signal amplification with MDAC, andtwo types of ring amplifiers: pseudo-differential and fully-differential ringamplifiersare considered for the implementation of MDAC in cyclic ADC.Theoretical analysis results show that power of thermal noise in MDACwith a pseudo-differential amplifier is much higher than that with a fullydifferentialring-amplifier. SPICE simulation results with transient noiseanalyses also show the similar trend. Experimental prototype cyclic ADCsin 65nm CMOS technology are implemented with the same architectureand the same circuit components except for amplifiers. Comparison of themeasured results of the two ADCs confirms the validity of the theoreticalanalysis results.
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