Editing SPICE (section)

=== Analyses ===
SPICE2 includes these analyses:
* AC analysis ([[linear]] [[small-signal model|small-signal]] frequency domain analysis)
* DC analysis (nonlinear [[quiescent point]] calculation)
* DC transfer curve analysis (a sequence of nonlinear operating points calculated while sweeping an input voltage or current, or a circuit parameter)
* Noise analysis (a small signal analysis done using an adjoint matrix technique which sums uncorrelated noise currents at a chosen output point)
* [[Transfer function]] analysis (a small-signal input/output gain and impedance calculation)
* Transient analysis (time-domain large-signal solution of nonlinear differential algebraic equations)

Since SPICE is generally used to model circuits with [[nonlinear element]]s, the small signal analyses are necessarily preceded by a [[quiescent point]] calculation at which the circuit is linearized. SPICE2 also contains code for other small-signal analyses: [[sensitivity analysis]], [[Pole–zero plot|pole-zero analysis]], and [[small-signal]] [[distortion]] analysis. Analysis at various temperatures is done by automatically updating semiconductor model parameters for temperature, allowing the circuit to be simulated at temperature extremes.

Other circuit simulators have since added many analyses beyond those in SPICE2 to address changing industry requirements. Parametric sweeps were added to analyze circuit performance with changing manufacturing tolerances or operating conditions. Loop gain and stability calculations were added for analog circuits. [[Harmonic balance]] or time-domain steady state analyses were added for RF and switched-capacitor circuit design. However, a public-domain circuit simulator containing the modern analyses and features needed to become a successor in popularity to SPICE has not yet emerged.<ref name="SPICE4"/>

It is very important to use appropriate analyses with carefully chosen parameters. For example, application of linear analysis to nonlinear circuits should be justified separately. Also, application of transient analysis with default simulation parameters can lead to qualitatively wrong conclusions on circuit dynamics.<ref>{{cite book |first=Giovanni |last=Bianchi |title=2015 7th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT) |arxiv=1506.02484| date = 2015 |chapter= Limitations of PLL simulation: hidden oscillations in SPICE analysis |pages=79–84 |doi=10.1109/ICUMT.2015.7382409 |isbn=978-1-4673-9283-9 |s2cid=7140415 }}</ref>