Abstract: An optimal design of CMOS in fully differential two stage OTA is presented in this paper. The OTA contains a folded-cascode input stage and a common-source output gain stage. Cascode compensation technique and switched capacitor common mode feedback technique are used. The distribution of zero-pole and settling performance of the OTA are analyzed. The MATLAB optimization program can find the optimal damping factor and natural frequency that makes the settling time of OTA in minimum quickly. The results of Cadence Spectre show that the OTA satisfies all the requirements of the system.