Continuous-Time Common-Mode Feedback Circuit for Applications with Large Output Swing and High Output Impedance

Motivated by the fact that no existing common- mode feedback block (CMFB) can work for the systems characterized with both high output impedance and large output swing, a new CMFB topology is introduced in this paper to accomplish this task. Various types of CMFB are studied, analyzed and simulated. Compared with other CMFBs, the proposed CMFB obtains the widest linear input range, smallest output common-mode level error, largest (full) output swing and has no interference to the system output impedance. All these properties entitle the presented CMFB circuit to suit all types of fully differential systems, especially for systems which require both high output impedance and large signal output swing.