0.65V sigma-delta modulators

/spl Sigma//spl Delta/ modulators for portable applications are presented operating within a large range of supply voltages. A 2/sup nd/ order and a cascaded 3rd order modulator are designed in Switched-Opamp (SO) technique with common mode level shift. The circuits are realized in a 0.18/spl mu/m CMOS process and occupy an area of 0.096 mm/sup 2/ and 0.139 mm/sup 2/, respectively. Neither low-V/sub T/ devices nor voltage boosting techniques are used. Proper operation is obtained down to a supply voltage of 0.65V.