A class of electronic systems containing both analog and digital subsystems whose most common application is to the conversion of analog signals to digital form and vice versa. The device is also known as a delta-sigma converter. The main advantage of the sigma-delta approach to signal conversion is its minimal reliance on the quality of the analog components required. To achieve this end, the system uses pulse density modulation to create a high-rate stream of single-amplitude pulses. For analog-to-digital conversion, the rate at which the pulses are generated depends on the amplitude of the analog voltage being sensed. For digital-to-analog conversion, the pulse density depends on the numeric digital quantity applied at the converter input.