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A general description of nonlinearities in pseudo differential operational transconductance amplifiers (OTA) with common-mode feedback (CMFB) is introduced. The effects of CMFB nonlinearities on the differential signals are evaluated and design tradeoffs including nonidealities are determined. A practical pseudo differential fully balanced fully symmetric OTA architecture with common-mode feedforward (CMFF) is used as a case study to probe the theory. The OTA has an inherent common-mode detector; hence, the CMFB circuit is efficiently implemented. The OTA is used to implement a 100-MHz fourth-order linear-phase OTA-C filter.
Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on (Volume:50 , Issue: 10 )
Date of Publication: Oct. 2003