Switched-capacitor band-pass filter of a discrete-time type, in particular for cancelling offset and low-frequency noise of switched-capacitor stages

摘要

A band-pass filter made up by an operational amplifier (2) and by an input circuit. The input circuit is formed by a capacitive filtering element (C 1 ), connected to the input of the operational amplifier; a coupling switch (11), coupled between an input node (10) and the capacitive filtering element; a capacitive sampling element (C s ), coupled between the input of the filter and the input node; and a sampling switch (16), coupled between the input node and a reference-potential line. The coupling switch and the input sampling switch close in phase opposition according to a succession of undesired components sampling and sensing steps, so that the capacitive sampling element forms a sampler for sampling the undesired component in the undesired components sampling step, in the absence of the component of interest, and forms a subtractor of the undesired components from the input signal in the sensing step.