AC Analysis Setup
You can perform AC analysis on these components:
- Passive
- Electrical cources (except for Fourier source)
- Switches (except for controlled switches)
- Semiconductor system level
- Semiconductor device level
- SPICE compatible models
- Transformers
- Continuous blocks
- Discrete blocks
- Source blocks
- Signal processing blocks (except for MAX, MIN, MAXT, MINT, two-point element with hysteresis)
- Math blocks
- Measurement (electrical domain)
- Time functions
- Characteristics
- Equations (except for DES solver)
- C-Models with definition for DC and AC simulation
- Macros using appropriate models (internal components, C-Models)
The following components are not supported for AC analysis:
- Electrical machines
- State graph
- Signal characteristics
- Physical domain
- Digital components
- Time functions
- Simulator parameters
Warning:
If models without DC and AC implementation are used in an AC simulation, an error message appears.
The AC Simulator calculates the simulation model in the frequency domain. The AC Simulator first performs a DC simulation (to calculate operation point values) and an AC simulation (for a given frequency range). The voltage and current information for the DC simulation and the values for the AC simulation are saved in one .sdb file
Use the AC Analysis Setup dialog box to access the following options:
- Analysis Setup Name – The default name is AC. If you specify additional solution setups, the default name increments by 1 (for example, AC1).
- Analysis Control – Includes values for Start Frequency - FStart, Stop Frequency - FEnd, Frequency time step or Points per decade - Fstep (depending on the AC sweep type - linear or decadic). Use the check box to disable the analysis.
Enable continue to solve causes the simulation to pause at the currently set stop frequency and to prompt you to set a new stop frequency (FEnd) to continue the simulation. See Progress Bar Menu for additional information.
If a simulation ends before the specified stop frequency (FEnd) is reached, the simulation does not pause and the Progress bar closes normally.
- Analysis Options – Opens a Select Solution Options dialog box where you can choose the solution option to use for an analysis.
AC simulation is based on small-signal analysis. In small-signal analysis, first a DC analysis is performed to find an operating point. By linearizing at the operating point, small-signal models for all nonlinear devices are analyzed over a user-specified range of frequencies.
It is important to note that the voltage- and current-dependent source nonlinear expressions (that is, when you select the AC use check box) are evaluated at the DC operating point and linearized at the operating point for AC analysis. For VHDL models, simultaneous statements must only be expressed purely as time domain equations, and will be linearized at the operating point for AC analysis.
Related Topics
Setting the Active Analysis Setup
Disabling/Enabling an Analysis Setup