Automatic symbolic simplification of analog circuits in MATLAB using ant colony optimization

In this paper, we present a MATLAB program for automatic symbolic simplification of analog circuits containing MOSFETs, using modified nodal analysis (MNA) and ant colony optimization (ACO). At first, all MOSFETs are replaced by the corresponding small-signal models. Then, the circuit be analyzed by applying symbolic MNA, and the exact symbolic expression of the circuit behavior is generated. The derived exact symbolic expression then be simplified using ACO. In this paper, a new criterion was introduced to minimize the mean square error (MSE) between the exact expression and the simplified one. The main advantage of proposed criterion is that final simplification error rate is controllable by user. In this way, the gain and phase MSEs across different frequencies were considered to evaluate the solutions generated by artificial ants. It is remarkable that all processing containing netlist text processing, symbolic analysis, post-processing and simplification are consecutively derived in MATLAB. Comparing the obtained numerical results with HSPICE demonstrates the efficiently of proposed tool.