On the power-efficiency of the gainless open-loop SC-circuit

The article presents the charge transfer models and the related current consumption efficiency figures of the gainless open-loop signal processing circuit. The presentation starts with a short overview on the factors that set the current consumption of the SC-circuit and the problems related to the minimization of it. The emerged issues suggest that the overall minimization of the current consumption of the SC-circuit that is intended to operate with a wide sampling frequency range may only be accomplished if the charge transfer is carried out in an open-loop configuration. An example case of such open-loop circuit is presented. The good charge transfer efficiency of the given open-loop topology is proven by deriving the boundary equations that describe the charge transfer process of the topology and calculating the typical current consumption/charge transfer efficiency figures by using the derived equations. The optimization of the circuit and the needed capacitance and transconductance models are briefly discussed. Finally, the presented theory is verified by comparing the measured efficiency figures of the realized 10-bit SigmaDelta-A/D-converter to the efficiency figures calculated using the given mathematical model