A sigma-delta modulator as an A/D converter

A sigma-delta modulator system is discussed as an alternative to the dual-slope converter. A simple auto-zero circuit and cold switching of the gain setting can be obtained. The implementation of the analog system in the form of two bipolar IC's offers an attractive application as a multi-input data acquisition system with a scanning capability. A combination with a D/A converter increases the resolution with a small Increase in conversion time. Hardly any accurate elements are required in this application if the dynamic element matching method is used in the D/A converter.