A Topology of Class-AB OTA with Increased DC-Gain and Slew-Rate

The Operational Trans- conductance Amplifier (OTA)is a main building block in several analog signal and mixed- signal integrated circuits. This paper, a novel low power Class- AB CMOS Operational trans- conductance amplifier (OTA) with High gain and high slew rate is presented. The proposed two-stage OTA, the characteristics of class-AB are applied in both of the stages. The Use of active loads for the first stage provides the effective transconductance boosting and increased,DC-gain product. The nonlinear current mirrors boost the current of the second stage leading to the increase of the slew rate. The OTA canbe employed in low- voltage low- power circuits requiring a good performance/power tradeoff.Theoretical analysis and Cadence simulations prove the performance of the new OTA. The simulation results indicate that the DC gain is improved by abot 13db.The UGBW and phase margin of the proposed OTA are 305 MHZ and 65º ,respectively.