1.3.2 New Features: A More Detailed Description

The most noticeable changes between Analog Insydes versions 1 and 2 were made to the circuit description and modeling language and to the way circuit equations are set up, stored, and presented to the user:

Netlist Format

The circuit description language (netlist format) was extended by functionality for managing device model parameter sets (model cards), global parameter settings, initial conditions, and multiple source values for different analysis modes (AC, DC, transient). With these enhancements it is now possible to represent all netlist and device model information contained in a SPICE circuit description consistently in an Analog Insydes Circuit object.

The netlist fragment shown below illustrates the use of some new language features. Note that the unspecific arguments of the keywords Model, Selector, and Parameters in the value field of the device reference Q1 permit an easy selection of device models and parameter sets at run time using Mathematica's pattern rewriting functionality. The model expansion mechanism of Analog Insydes 2 makes use of this approach to automatically select appropriate device models according to the specified analysis mode.

Analog Insydes 2 netlist fragment

amplifier = Circuit[

Netlist[

{V1, {1, 0}, Symbolic -> V1,

Value -> {AC -> 1, DC -> 2.5,

Transient->SinWave[Time, 2.5, 0.1, 1000]}},

{Q1, {2 -> C, 1 -> B, 3 -> E},

Model->Model[BJT, NDEF, Q1],

Selector -> Selector[BJT, NDEF, Q1],

Parameters -> Parameters[BJT, NDEF, Q1],

GM$ac -> 0.02, RPI$ac -> 5.0*10^3, },



],

ModelParameters[Name -> NDEF, Type -> NPN,

IS -> 10^-16, BF -> 100, BR -> 1, VAF -> 150],

GlobalParameters[TEMP -> 300, GMIN -> 10^-12]

]

Circuit Equations

In Analog Insydes 1, symbolic circuit equations and corresponding numerical information (design point, initial conditions, etc.) were not handled in a consistent fashion. To prevent errors due to potentially inconsistent data and to provide a unified and more user-friendly mechanism for managing all additional data associated with a system of symbolic circuit equations, the internal representation of circuit equations was fundamentally changed in version 2. Now, all equation setup and circuit analysis functionality is centered around a common data structure, the DAEObject.

A DAEObject is generated by means of the command CircuitEquations. It represents a linear or nonlinear system of differential-algebraic equations (DAE) along with numerical data needed for numerical analysis or symbolic approximation. In addition, a DAEObject contains information about the type of equations it represents (AC/DC/transient, MNA/STA) plus a snapshot of all relevant option settings taken at the point of time when the equations were set up. This data encapsulation approach ensures the consistency of all data belonging to a particular circuit analysis context and reduces the number of parameters that need to be passed to functions which operate on circuit equations.

Interfaces

Analog Insydes 2 provides several new or improved modules for interfacing with commercial circuit design environments. Platform-independent netlist converters with small-signal data and model-card import functionality are now available for a variety of widely used circuit simulators, including PSpice, Saber, and Eldo. Waveforms can be imported from PSpice, Saber, and Eldo data files. Circuit schematics can be imported into Mathematica via a DXF file converter. Moreover, Analog Insydes 2 features a model writer which is capable of generating behavioral model templates (e.g. Saber MAST) automatically from a DAEObject.

Modeling Language

As a consequence of the requirements identified during recent work on symbolic modeling and analysis of nonlinear circuits, the behavioral modeling capabilities for nonlinear dynamic systems were substantially extended. With the enhanced model description format of Analog Insydes 2, it is now possible to designate model port nodes as optional, to specify default values for model parameters as well as initial conditions and guesses for model variables, and to control how design-point information is generated for symbolic parameters of model equations.

Library Concept

Based on the modeling language extensions described above, a completely new device model library concept was designed for Analog Insydes 2. PSpice and Eldo compatible models are available for R, L, C, D, BJT, MOS, and JFET devices. Three model simplification levels can be selected when setting up circuit equations to control the complexity of symbolic analysis.

Nonlinear Symbolic Analysis

Completely new functionality has been implemented for symbolic analysis and approximation of nonlinear circuits. Based on a flexible user interface, the approximation routines allow an arbitrary choice of analysis and error-control functions. In combination with the new model writer, Analog Insydes 2 can be used for automated generation of nonlinear behavioral models.

Pole/Zero Analysis

Efficient numerical pole/zero and root locus analysis is now supported through two different generalized eigenvalue problem solvers: an enhanced version of the QZ algorithm and a variant of the Jacobi orthogonal correction method (JOCM). The introduction of the DAEObject concept reduces the amount of parameters passed to functions. In addition, a new matrix-based method for symbolic pole/zero analysis has been implemented. The algorithm simplifies a symbolic generalized eigenvalue problem with respect to a selected root, using the JOCM for efficient iterative error tracking.

User Interface

The use of Analog Insydes 2 has been considerably simplified by combining many frequently used steps in powerful macro commands and providing more default actions. With as few as three Analog Insydes commands it is possible to set up and run circuit analyses from PSpice, Eldo, or Saber netlists. In addition, the external binaries (QZ algorithm, matrix approximation) have been fully integrated into Analog Insydes 2 and can be used transparently like built-in commands.

Multi-Platform Support

Multi-platform support is available for all binaries: One Analog Insydes installation can be accessed from different platforms. Transparently for the user the correct binaries are automatically chosen. This allows for installing Analog Insydes on a site-wide file server and simultaneously using it from different platforms.