Digital filter and oversampling analog to digital converter employing the same

摘要

A digital filter has a cut-off frequency which can be varied by a simple control circuit. The digital filter includes a tap coefficient setting section and a convolution calculation section. The convolution calculation section is constructed so as to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients or same input data and then varying the tap coefficient or the input data to allow the repetitive convolution calculation to be repeated subsequently. The digital filter can be applied to an oversampling analog to digital converter.