COMMON-MODE FEEDBACK BIAS GENERATOR FOR OPERATIONAL AMPLIFIERS

A common-mode feedback circuit comprises a reference generator (12) for generating a signal corresponding to a desired common-mode operating point connected to a common-mode bias circuit (14) for generating a second signal corresponding to the common-mode operating point of the outputs (V.sub.out.sup.+, V.sub.out.sup.-) of the fully differential operational amplifier. In the preferred embodiment, the common-mode bias circuit (14) includes a sensing circuit (58) comprising two MOS transistors (60, 62) having sources and drains connected together. The MOS transistors (60, 62) operate in the ohmic region to provide a variable load responsive to the output signals (V.sub.out.sup.+, V.sub.out.sup.-) connected to their gates.