PartSim Online Circuit Analysis Simulator by Aspen Labs
Program with Integrated Circuit Emphasis (SPICE) has been around since 1973. The basic computational engine has always
been open source. It began as a simple analog circuit simulator that took a structured text file as the input net
list and provided a text file output that contained the calculated values that the user specified such as DC bias
points, transient analysis, and AC analysis. Component models started with relatively simple definitions. If you wanted
a graph of the response, it was in the form of text characters with a standard 80-column division on the y-axis and
the x-axis was as many divisions as it needed to be to cover all the points calculated (often printed out on fan-fold
paper in a pin printer). Yes, I personally used those versions in the mid 1980s.
As time progressed, improvements
were added to the computational engine to handle a wider range of component models including digital and RF/microwave.
More parameters were added to component models to yield a better agreement between simulation and laboratory measurements.
Lagging the mathematical sophistication was development of a graphical user interface (GUI) for building circuit schematics
rather than needing to enter all the circuit nodes and component parameters manually into a text file. Trying to keep
track of node numbers was a real challenge for all but the simplest circuits. Early attempts at a GUI were cumbersome
and did not provide a seamless interface between schematic entry and simulation and graphing. Eventually really good
solutions came to the market. Most of the modern circuit simulators are based on SPICE, with proprietary add-ons in
the computational engine. User interfaces have gotten really nice. The more you're willing to pay, the better the
interface and the calculation capability.
Online simulators are now going through the same kinds of growing
pains that the earlier iterations of PC-based SPICE simulators experienced. Most are really clunky and always seem
to be missing key features and/or easily accessed features - like rotating components on the schematic or routing
interconnect lines. Aspen Labs has a free online analog circuit simulator called
PartSim that seems to have conquered most of the basics. Being
able to save and recall your work is a huge benefit. However, it appears that the file is saved on the website server
rather than on your local machine, so privacy and security issues might prevent a few users from using such a service
regardless of how good it is. I have recommended online tools to people in the past and have been apprised of the
proprietary information problem. Still, most users probably will not care. One advantage of the online storage is
that it is effectively a 'cloud' environment where you can access your circuit file from anywhere that has an Internet
connection (after signing in with user name and password).
I loaded the example files and played around with
them enough to know that PartSim is just what the hobbyist and
casual professional designer can use. Simulation time and switching between screens is slower than with a local program,
but that is more a function of your Internet connection than of PartSim's host server. There is no sense in me reiterating
what has been written a thousand times about how to enter circuits and set up and run simulations, so instead I refer
you to the seven short online video tutorials to help get you started. There
are some not-so-obvious features that makes it worth your while to view them. If you are not the type to read instructions,
just remember to right-click and double-click on everything - including interconnect lines - to find all the options
available to you.
18 years old or older. I could understand the need if it was an astronomy simulator with
but this is puzzling.
These items are an archive of past Topical Smorgasbord items that have appeared on the RF Cafe homepage. In keeping with
the "cafe" genre, these tidbits of information are truly a smorgasbord of topics. They all pertain to topics
that are related to the general engineering and science theme of RF Cafe.