Patent ID: 7256720

Claim:
An output filter for a delta sigma modulator, comprising: a first and a second constant current source having first and second outputs, respectively; a FIR filter having a plurality n of delay element arranged in cascade, where n is a whole number greater than two, each element being operative to output data of the delta sigma modulator by controlling currents via n switches from the first and second constant current sources on the basis of each of the output data to thereby generate a plurality of weighted currents that are weighted according to a filter characteristic, the weighted currents being added separately for inverted and non-inverted signals and outputted separately at an output side of the FIR filter; and a current-to-voltage conversion unit, said unit having an input side coupled to the output side of the FIR filter and comprising a full differential operational amplifier and feed back resistors, said amplifier having a pair of inputs, each input coupled to a respective one of each separate output of said FIR filter and having an output side.