The convergence problem in SPICE

Although SPICE has existed for over fifteen years, as yet, there is still no other candidate analogue simulator to replace it. Today, many thousands copies of SPICE and its derivatives are being used world-wide, making it the most successful design tool-kit for analogue designers ever developed. However, despite its universal acceptance, complaints from SPICE users are not uncommon. One of the most troublesome problems concerns convergence. It is helpful for users to have some knowledge about the algorithms used in SPICE, and therefore understand how to use the techniques, i.e. use of OPTIONS, which are provided by SPICE to alleviate convergence problems. The most annoying error of SPICE is `no convergence in DC analysis´ or `internal time step too small´. Actually the latter case in transient simulation is a superset of the problem of DC convergence. In analysing the cause of the convergence problem, it is necessary to review the SPICE algorithm first