The simulation errors introduced by the SPICE transient analysis

The SPICE transient simulations of simple circuits that can be easily solved by hand often give erroneous results. The numerical errors are investigated and analyzed using the analogy of the simulation program with a digital integrator. The transfer function of the digital integrator is defined through the z-transform. The solving method implemented in SPICE is one of the possible approximations of the z-transform. This approximation has some good properties but also some drawbacks; it warps the frequency and it is not step invariant. >