A sigma-delta ADC (Analog-to-Digital Converter) is a type of converter that transforms analog signals into digital data. It works by oversampling the input signal and using a feedback loop to create a high-resolution digital output. This method allows for better noise reduction and improved accuracy in capturing the signal. The core of a sigma-delta ADC consists of a modulator and a digital filter. The modulator continuously samples the input signal and generates a bitstream that represents the signal's average value. The digital filter then processes this bitstream to produce a precise digital representation of the original analog signal.