The floating capacitor as a differential building block

Abstract

This paper analyzes the advantages and limitations of using the floating- (or flying-) capacitor technique as a building block with differential input and either differential or single-ended output to implement voltage amplifiers, multiplexers, and coherent amplitude demodulators. Theoretical analysis, supported by experimental results, shows that the fully differential configuration has a better common-mode rejection ratio (CMRR). However, if the output signal, once amplified, must be single ended, then it may be better to have a floating capacitor with single-ended output in amplifiers and some multiplexers whereas in demodulators a floating capacitor with differential output yields a better CMRR.