A continuous-time common-mode feedback circuit (CMFB) forhigh-impedance current-mode applications

摘要

A continuous-time common-mode feedback circuit (CMFB) isnpresented. A two-stage high-gain architecture is used to stabilize andnminimize the offset of the common-mode voltage. A long-channelndifferential-difference amplifier (DDA) input stage enables this CMFBncircuit to have a wide input voltage range without a serious linearitynproblem. A special compensation scheme enables this circuit to be usednin high-impedance current-mode systems without a stability problem. Thisncircuit has been implemented within a continuous-time switched-currentnΣΔ modulator in a 2 Μm CMOS process. It achieves an±1 V input voltage range with an active area of 100nΜm×60 Μm and a power dissipation of 270 ΜW from a singlen5 V power supply