A fuzzy logic based approach for parametric optimization of MOS operational amplifiers

In this work, we have used the concept of fuzzy logic to build a CAD tool for the parametric optimization of MOS operational amplifiers (op-amps). In order to capture human intentions to express the requirements for a particular application, e.g. minimize power, maximize gain, etc., each of the performance specifications of a given topology is assigned a membership function to measure the degree of fulfillment of the objectives and the constraints. A number of objectives are optimized simultaneously by assigning weights to each of them representing their relative importance, and then by clustering them to form the objective function, which is solved by Powell's direct search algorithm. After optimization, the program creates a SPICE netlist of the circuit topology for the verification of the design. Initially, this approach was used for parametric optimization of simple bipolar and MOS circuits, e.g. current mirrors, gain stages, differential amplifiers, etc. Encouraged by these results, it was applied to much more complex blocks, such as op-amps. The design results obtained from our optimization program showed an excellent agreement with those obtained from SPICE simulation for the op-amp topologies considered in this work.