High Performance Op Amp Design – Review

In a never-ending effort to reduce power consumption and gate oxide thickness, the integrated circuit industry is constantly developing smaller power supplies. Furthermore, in an effort to reduce costs and integrate analog and digital circuits onto a single chip, MOS devices are used in the weak inversion region or the subthreshold inversion region to minimize dc source power. A feasible configuration for high gain, low power op amp design utilizing subthreshold operation along with active operation is proposed. This paper discusses and compares the existing compensation methods for operational amplifiers. In this paper comparison is made between different methodologies of op amp design , such as Nested Miller Compensation Method, Feedforward Compensation technique. Two stage and Three stage op amp using Nested Miller Compensation method, adaptive biasing CMOS op-amp with enhanced DC gain ,Three stage op amp using Indirect Compensation technique. The comparison table 1, shows that the nested miller compensation method provides a high gain of 114.3 dB, high uniy gain bandwidth of 103Mhz, and the low power consumption of about (< 3 mW) ,As compared to the other methods. And feedforward compensation method is also have a low power consumption of upto 18 mW, and it requires a low power suppy of 1.2V.