Symbolic approximation of circuit response containing negative terms

Symbolic analysis of linear analog circuits and systems can generate symbolic expressions too large and complicated to use or interpret. Very often, majority of the terms in the full symbolic expression are relatively unimportant, and only a small number of dominant terms determines the circuit/system behavior and helps gain insight into this behavior. This paper presents a new algorithm for symbolic approximation of analytic expressions representing the circuit response. Its implementation in Mathematica, the program NeglectD, is also exposed. The algorithm takes into account the negative terms of symbolic expressions. Symbolic approximation is carried out based on magnitudes of terms when some or all circuit parameters are specified by their nominal values. The proposed implementation is illustrated by examples.