A delta sigma analogue to digital converter comprising: an integrator having first and second differential inputs for receiving an input analogue signal, the integrator having differential outputs; a quantiser having first and second differential inputs which receive signals output by the integrator, and an output which provides a digital output signal of the delta sigma analogue to digital converter, and a digital to analogue converter. The digital to analogue converter has an input which is connected to an output of the delta sigma analogue to digital converter, and first and second differential outputs. The first output of the digital to analogue converter is connected to the first input of the integrator such that if the second output of the digital to analogue converter is not connected to the second input of the integrator and the second input of the integrator is connected to a fixed reference voltage the delta sigma analogue to digital converter is able to operate in a single-ended mode.