A feedback coder, which employs simple CMOS push/pull amplifiers as gain elements, along with a bistable circuit, in its preferred embodiment takes the form of a second-order delta-sigma modulator. The output of the modulator is converted into pulse code modulated words by a finite impulse response filter...http://www.google.fr/patents/US4860012?utm_source=gb-gplus-shareBrevet US4860012 - Integrated analog-to-digital converter
