Design And Resizing Of CMOS Operational Amplifiers Based On Operating Point Driven Method

With the rapid development of integrated circuit,the integration level of circuits and systems is increasing and the era of system on chip(SOC)has come.It is well known that the bottleneck of the design of a SOC is its analog part.Therefore,improving the level of analog design automation is an important issue in the IC design.This thesis deals with the automatic design of analog integrated circuits based on the operating point driven method.In the traditional optimization based analog circuit design automation,the transistor sizes are taken as the design variables.Instead,a set of independent DC currents and voltages at the operating point of the circuit are taken as the design variables in the operating point driven method.There are a number of benefits with this change of the design variables,among which the most important is convenient representation of the constraints of the transistor's working states.A method to determine a set of independent operating point voltages and currents in a CMOS analog circuit is presented in this thesis.Firstly,a set of topologically independent gate-source voltages and drain-source currents is found based on the tree searching in the voltage and current graphs of the circuit.Secondly,symmetrical structures in the circuit are identified by the labeling algorithm performed on the associated bipartite graph of the circuit,and the correlated voltages and currents caused by the symmetries are deleted.The algorithm then carries out the sizing of all the transistors under the given settings of these independent gate-source voltages and drain-source currents.By using the inversion of the BSIM like MOSFET model in the determination of the transistor sizes,the operating point of the circuit so obtained is matched exactly with the values specified by the designer.The design solution so obtained is always a good initial point for further optimization of the circuit performances.A number of design examples are provided to verify the effectiveness of the method.Based on the positive results of the verification,the algorithm is further applied to the automatic migration of circuits between different processes based on the gm/Id methodology,and the validity is demonstrated by two examples.