Sigma delta modulator and method therefor

A method for converting an analog input signal to a digital signal, the method comprising:

• receiving an input analog signal;
• subtracting a feedback analog signal from the input analog signal in a summing junction to produce a subtracted signal;
• filtering the subtracted signal to generate a first filtered signal by a low pass filter;
• generating a second filtered signal by an active filter, a single-OpAmp resonator, or an integrator;
• converting the second filtered signal to a digital output signal by sampling at a predetermined sampling frequency;
• feeding back the digital output signal to the summing junction via a digital-to-analog converter, DAC, converting the digital output signal to the feedback analog signal.

A sigma delta modulator, comprising:

• an input configured to receive an input analog signal;
• a summing junction coupled to the input, configured to subtract a feedback analog signal from the input analog signal;
• a first stage including a low pass filter coupled to the summing junction, wherein the low pass filter is configured to generate a first filtered signal;
• a second stage coupled to the low pass filter and configured to generate a second filtered signal by an active filter, the second stage including a first RC network coupled between the low pass filter and the amplifier, a second RC network coupled between the input of the amplifier and the output of the amplifier, and a third RC network coupled between the input of the amplifier and the output of the amplifier, wherein the active filter comprises at least one amplifier where the first filtered signal is chopped at a chopping frequency which is 1/N times of a predetermined sampling frequency;
• a back-end stage coupled to the second stage, wherein the back-end stage comprises an analog to digital converter configured to convert the second filtered signal to a digital output signal by sampling at the predetermined sampling frequency;
• and
• a feedback path for routing the digital output signal to the summing junction, wherein the feedback path comprises a digital to analog converter, DAC, converting the digital output signal to the feedback analog signal.