Sigma-delta analog-to-digital converter

A differential sigma-delta analog to digital converter (ADC) comprising

• a negative signal input and a positive signal input;
• a negative signal output and a positive signal output;
• a passive filter having a pair of filter inputs and a pair of filter outputs, each filter input coupled to a respective one of the negative signal input and the positive signal input;
• a gain stage having a pair of gain stage inputs and a pair of gain stage outputs, the pair of gain stage inputs being coupled to a respective one of the pair of filter outputs;
• a quantiser having a pair of quantiser inputs coupled to a respective one of the pair of gain stage outputs and a pair of quantiser outputs coupled to a respective one of the negative signal output and the positive signal output;
• wherein
• the passive filter comprises a filter resistor coupled between each respective filter input and filter output and a filter capacitor coupled between the pair of filter outputs;
• the sigma-delta ADC further comprises:
• a first feedback resistor coupled between the negative signal output and the filter output corresponding to the positive signal input;
• and a second feedback resistor coupled between the positive signal output and the filter output corresponding to the negative signal input;
• and
• the gain stage comprises a gain element having a pair of gain element inputs coupled to the pair of gain stage inputs and a pair of gain element outputs coupled to the pair of gain stage outputs and a series arrangement of a first gain stage capacitor, a first gain stage resistor, and a second gain stage capacitor coupled between the pair of gain element outputs.