Design and Analysis of Folded Cascode OTA

Abstract

The outside world is actually of analog nature and to be able to interact with computers etc., We need some amount of analog and moxed analog/digital circuits. Among various analog circuits Operational Amplifier has a very dominant role. It is used in almost all-analog applications. Its main characteristics are high input resistance, low output resistance, high gain, high CMRR, high unity gain bandwidth and high Common Moder Rage (CMR) etc. Performance of any analog application depends upon these characteristics, if they are meeting the desired specifications. Once the topology is been selected the main thing, which put impact on characteristics, is design (values) of components. A fully differential CMOS folded-casode OTA is analyzed and the results are presented in the form of design equations and procedures. in this study a CAD tool has been developed using Turbo C for determing the component values and transistor dimensions for CMOS Folded Cascode. OTA. Trade-offs among such factors as DC Garin, Unity Gain Bandwidth, Phase Margin, Output Swing, Slew Rate, Common Mode Gain PSRR and Offset etc are made evident. A number of Op-amp circuits have been simulated using Tanner tools. On the basis of simulation results the performance analysis has been done. A graphical representation of the relationships among the gain, phase margin for different capacitive loadings is presented to visually illustrate one form of desing optimization.