About PSpice
What is PSpice?
PSpice1 is a simulation program that models the behavior of a circuit containing any mix of analog and digital devices. You can think of PSpice as a software-based breadboard of your circuit that you can use to test and refine your design before ever touching a piece of hardware.
Because the analog and digital simulation algorithms are built into the same program, PSpice simulates mixed-signal circuits with no performance degradation because of tightly coupled feedback loops between the analog and digital sections.
PSpice can perform the following types of analyses:
- AC, DC, and transient analyses, so you can test the response of your circuit to different inputs
- Parametric, Monte Carlo, and sensitivity/worst-case analyses, so you can see how your circuits behavior varies with changing component values
- Digital worst-case timing analysis to help you find timing problems that occur with only certain combinations of slow and fast signal transmissions
Models
PSpice includes model libraries that feature over 15,000 analog and 1,600 digital models of devices manufactured in North America, Japan, and Europe. Among these libraries are numerous models with parameters that you can tweak for a given device. These include independent temperature effects.
PSpice also supports analog and digital behavioral modeling, so you can describe functional blocks of circuitry using mathematical expressions and functions.
The range of models built into PSpice include not only those for resistors, inductors, capacitors, and bipolar transistors, but also the following:
- transmission line models, including delay, reflection, loss, dispersion, and crosstalk
- nonlinear magnetic core models, including saturation and hysteresis
- eight MOSFET models, including BSIM4 version 4.1, BSIM3 version 3.2, and EKV version 2.6
- five GasFET models, including Parker-Skellern and TriQuints TOM2 model
- IGBTs
- digital components with analog I/O models
Related Topics
What is Probe?
After completing the simulation, PSpice plots the waveform results so you can visualize the circuits behavior and determine the validity of your design. You can use the waveform analysis features of PSpice to visually analyze and interactively manipulate the waveform data produced by circuit simulation. This built-in waveform analyzer is referred to as Probe.
Probe uses high-resolution graphics so you can view the results of a simulation both on the screen and in printed form. On the screen, waveforms appear as plots displayed in Probe windows within the PSpice workspace.
In effect, waveform analysis is a software oscilloscope. Performing a PSpice simulation corresponds to building or changing a breadboard, and performing waveform analysis corresponds to looking at the breadboard with an oscilloscope. Taken together, simulation and waveform analysis is an iterative process. After analyzing simulation results, you can refine your design and simulation settings and then perform a new simulation and waveform analysis.
With waveform analysis you can:
- view simulation results in multiple Probe windows
- compare simulation results from multiple circuit designs in a single Probe window
- display simple voltages, currents, power, and noise data
- display complex arithmetic expressions that use the basic measurements
- display Fourier transforms of voltages and currents, or of arithmetic expressions involving voltages and currents
- display analog and digital waveforms simultaneously with a common time base (for mixed analog/digital simulations)
- add text labels and other annotation symbols for clarification
What you can plot in Probe depends on the types of analyses you run. Bode plots, phase margin, derivatives for small-signal characteristics, waveform families, and histograms are only a few of the possibilities. You can also plot other waveform characteristics such as rise time versus temperature, or percent overshoot versus component value.
PSpice generates two forms of output: the simulation output file and the waveform data file. The calculations and results reported in the simulation output file act as an audit trail of the simulation. However, the graphical analysis of information in the waveform data file is the most informative and flexible method for evaluating simulation results. The waveform data file is used by Probe to generate the waveforms displayed in the PSpice workspace.
Related Topics
Types of analyses you can run with PSpice
Basic analyses
Click any of the following analysis types for more information:
Advanced multi-run analyses
The multi-run analyses-parametric, temperature, Monte Carlo, and sensitivity/worst-case-result in a series of DC sweep, AC sweep, or transient analyses, depending on which basic analyses you enabled.
Click any of the following analysis types for more information:
AC sweep and noise
These AC analyses evaluate circuit performance in response to a small-signal alternating current source. The table below summarizes what PSpice calculates for each AC analysis type.
DC sweep & other DC calculations
These DC analyses evaluate circuit performance in response to a direct current source. The table below summarizes what PSpice calculates for each DC analysis type.
Transient and Fourier
These time-based analyses evaluate circuit performance in response to time-varying sources. The table below summarizes what PSpice calculates for each time-based analysis type.
Parametric and temperature
For parametric and temperature analyses, PSpice steps a circuit value in a sequence that you specify and runs a simulation for each value. The table below shows the circuit values that you can step for each kind of analysis.
Monte Carlo and sensitivity/worst-case
Monte Carlo and sensitivity/worst-case analyses are statistical. PSpice changes device model parameter values with respect to device and lot tolerances that you specify, and runs a simulation for each value. The table below summarizes how PSpice runs each statistical analysis type.
Frequency Response Analysis
Frequency Response Analysis is typically used to get frequency response of the non-linear switching circuits having varying operating point. This analysis injects transient signals into the loop of interest and then extracts frequency data using Fourier analysis to plot gain/phase response.
Following options have been added in Capture – PSpice flow to enable Frequency Response Analysis:
-
MINSIMPTS
Specifies minimum number of time points used for a transient simulation. More the number of points better would be the output resolution.
To use MINSIMPTS, add the following comment text on the Capture Schematic:
@PSpice:
.options MINSIMPTS=1000 -
.PROBE64 P(<>)
Writes parameter defined using .PARAM command on the probe.
To use .PROBE64 command, add the following comment text on the Capture Schematic:
@PSpice:
.PROBE64 P(FREQ)
For more information on the usage of MINSIMPTS option and .PROBE64 command in Frequency Response Analysis, see the example at <Installation Directory> \tools\pspice\capture_samples\anasim\fra.
Files used by PSpice (input files)
To simulate your design, PSpice needs to know about:
- the parts in your circuit and how they are connected
- what analyses to run
- the simulation models that correspond to the parts in your circuit
- the stimulus definitions to test with
This information is provided in various data files.
Some of these are generated by schematic editors2, others come from libraries, and still others are user-defined.
Files Generated by Schematic Editors or Design Entry Programs
Capture is a design entry program in which you need to prepare your circuit for simulation. This means:
- placing and connecting part symbols
- defining component values and other attributes
- defining input waveforms
- enabling one or more analyses
- marking the points in the circuit where you want to see simulation results
For more information about designing circuits with Capture, see their respective online helps.
When you begin the simulation process, the design entry programs first generate files describing the parts and connections in your circuit. These files are the netlist file and the circuit file that PSpice reads before doing anything else.
The netlist file contains a list of the device names and their values, and the connections between the devices. The name that design entry programs generate for this file is DESIGN_NAME.net. The netlist file is located in the directory:
<project_directory>\worklib\<design_name>
The circuit file contains commands describing how to run the simulation. This file also refers to other files that contain netlist, model, stimulus, and any other user-defined information that apply to the simulation. The name that the design entry programs generate for this file is PROFILE_name.cir.
Other Input Files
Before starting the simulation, PSpice needs to read other files that contain simulation information for your circuit. These are model files, and if required, stimulus files and include files.
Related Topics
Model libraries
A model library is a file that contains the electrical definition of one or more parts. PSpice uses this information to determine how a part will respond to different electrical inputs.
These definitions take the form of either a:
- model parameter set, which defines the behavior of a part by fine-tuning the underlying model built into PSpice, or
- subcrcuit netlist, which describes the structure and function of the part by interconnecting other parts and primitives
The most commonly used models are available in the PSpice model libraries shipped with your programs. The model library names have a .LIB extension.
Stimulus files
A stimulus file contains time-based definitions for analog and/or digital input waveforms. You can create a stimulus file using a standard text editor, to create the definition (a typical file extension is .STM).
Include files
An include file is a user-defined file that contains:
You can create an include file using any text editor, such as Notepad. Typically, include file names have a .INC extension.
Preparing and configuring input files
You must first prepare the circuit design using Capture as the primary design entry program. Entering the design in Capture is the most efficient way to draw up the circuit and define the various parameters required for simulation. Once the circuit is entered in the design entry programs, you can configure the input files for analysis by PSpice.
Along with the netlist and circuit files generated by the design entry programs, PSpice searches model libraries, stimulus files, and include files for any information it needs to complete the definition of a part or to run a simulation.
How you configure your model libraries and other files determines the way PSpice uses those files. Much of the configuration is set up for you automatically. However, you can do the following yourself:
- add and delete files from the configuration
- change the scope of a file: that is, whether the file applies to one profile only, one design only (local) or to any design (global)
- change the search order
For more detailed information about designing circuits and configuring files, see the Capture Help.
Files generated by PSpice (output files)
After reading the circuit file, netlist file, model libraries, and any other required inputs, PSpice starts the simulation. As simulation progresses, PSpice saves results to two files-the waveform data file and the PSpice output file.
Waveform data file
The waveform data file contains simulation results that can be displayed graphically. PSpice reads this file automatically and displays waveforms reflecting circuit response at nets, pins, and parts that you marked in your schematic (cross-probing). You can set up your design so PSpice displays the results as the simulation progresses or after the simulation completes.
There are two ways to add waveforms to the display:
- from within PSpice, by specifying trace expressions
- from within the design entry programs, by placing markers for cross-probing
After PSpice reads the data file and displays the initial set of results, you can add more waveforms and perform post-simulation analysis of the data.
PSpice output file
The PSpice output file is an ASCII text file that contains:
- the netlist representation of the circuit
- the PSpice command syntax for simulation commands and options (such as the enabled analyses)
- simulation results
- warning and error messages for problems encountered during read-in or simulation
- the types of analyses you run
- the options you select for running PSpice
- the simulation control symbols (like VPRINT1 and VPLOT1) that you place and connect to nets in your design
Documentation
To access online documentation, you must open the Cadence Help window.
- From the programs folder in the Windows Start menu, choose PSpice for TI 2020 – PSpice for TI 2020 Help.
- From the Library pane, click the PSpice category to show the documents in the category.
- Double-click a document title to open that document.
You can also open PSpice specific documents by choosing Help – Documentation from the PSpice window.
Additional sources of information about PSpice
Recommended textbooks
Many textbooks and technical articles have been written in several languages about how to use PSpice when doing circuit analysis. The following is a brief list of some useful resources.
- Goody, Roy W., PSpice for Windows, A Circuit Simulation Primer, Prentice-Hall, 1995
- Goody, Roy W., PSpice for Windows, Vol. II, Operational Amplifiers & Digital Circuits, Prentice-Hall, 1996.
- Herniter, Marc E., Schematic Capture with PSpice, Macmillan, 1994.
- Kielkowski, Ron, Inside SPICE, Overcoming the Obstacles of Circuit Simulation, McGraw-Hill, 1994.
- Kielkowski, Ron, SPICE, Practical Device Modeling, McGraw-Hill, 1995.
- Tuinenga, Paul W., Spice, A Guide to Circuit Simulation & Analysis Using PSpice, 2nd Ed., Prentice-Hall, 1992.
- Depending on the license and installation, either PSpice or PSpice Simulator is installed. However, all information about PSpice provided in this manual is true for PSpice Simulator.
- Schematic editor or design entry programs refer to OrCAD Capture.
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