I am simulating a parasitic capacitance extracted toplevel circuit with UltraSim 6.0. I have a problem of DC operating point calculation. UltraSim says in output log that "DC simulation finishes without reaching steady state" at the beginning of transient simulation. Then all bias voltages begin to make their settling behavior to their final value, but it takes a lot of transient simulation time. Is there a method at UltraSim to calculate steady state operating point at the beginning of transient simulation correctly?
Thanks in advance,
You can try .usim_opt dc_prolong=1 which will extend the dc calculation until a stable operating point is reached.
See cdsnhelp Chapter 3 of UltraSim User Guide for more dc options and details.