Patent ID: 7362252

Claim:
A sigma-delta ADC modulator, comprising a receiving circuit for receiving an input signal and a feedback signal and generating a first difference signal corresponding to the difference of the input signal and the feedback signal; a plurality N of loop filter transconductors of rank q, with the loop filter transconductor of rank 1 coupled to the receiving circuit, where q ranges from 1 to N; a plurality N of feedforward weighting amplifiers for generating weighted signals, the feedforward weighting amplifier of rank q being coupled to the corresponding loop filter transconductor of rank q; a first adding element, coupled to the N feedforward weighting amplifiers, for receiving weighted signals and generating a filtered signal; at least an adjustable local feedback circuit, comprising: a feedback weighting amplifier which can be disabled and has an adjustable feedback coefficient, coupled to the loop filter transconductor of rank m+1, for receiving an output signal of the loop filter transconductors of rank m+1 and generating a local feedback signal, where m ranges from 2 to N−1; and a second adding element, coupled between loop filter transconductors of rank m−1 and m, for generating a second difference signal corresponding to the difference between an output signal of the loop filter transconductor of rank m−1 and the local feedback signal; a quantizer, coupled to the first adding element, for quantizing the filtered signal and generating a digital output signal; and a feedback DAC, coupled to the quantizer and the receiving circuit, for generating the feedback signal according to the digital output signal; characterized in that the bandwidth of the sigma-delta ADC modulator can be tuned by changing the feedback coefficient of the feedback weighting amplifier.