In this paper we consider two important fundamental techniques for large-scale circuit analysis. In the first technique, unilateral subcircuit models are considered which we call one-way models. With these models, the independent time integration of the subcircuits can be accomplished. The second technique which is called a time waveform technique is based on the one-way macromodels. In this approach the subcircuits are integrated for the total analysis time in contrast to the conventional incremental time approaches where all circuits are integrated simultaneously by small incremental time steps. © 1982 IEEE.