Symbulator 9

the best portable symbolic simulator of linear circuits

New! Symbulator 9 for Python and SymPy

Solve circuits with the letters still in them.

Give Symbulator symbols instead of numbers and it hands back algebra — every node voltage, every element current, every power, in terms of whatever you left unknown. Describe the circuit an element at a time and ask it what you want to know.

Use it online Learn how to

Start here

Run it in a browser tab, or put it on your own machine.

Symbulator 9 is the current version, built on Python and SymPy. Every route below runs the same program.

Use it

  • Nothing to install

    Run Symbulator online

    Opens in a browser tab and runs straight away, on anything with a screen. The quickest way to try Symbulator, and enough for most coursework.

    symbulator.pythonanywhere.com

Or install it, and work offline

  • Including phones and tablets

    Install from the browser

    A web page that installs Symbulator 9 onto your device for you. It is the installer, not the program — once it has done its job, Symbulator runs on your device and needs no connection.

    Works on phones, tablets and computers

    install.symbulator.com

  • Unpack it yourself

    Download the zip

    The same program as a plain archive, to put where you want it. Use this if you would rather see what you are installing, or install it somewhere the browser cannot reach.

    Works on Windows, macOS and Linux

    symbulator.com/9/local.zip

Learn it

  • Fourteen lessons, with worked problems

    Read the documentation

    From describing your first circuit to transient analysis, three-phase and two-ports — every lesson worked through against real textbook problems.

    learn.symbulator.com

  • For the curious: how it works inside

    The Internal Logic of Symbulator

    A monograph on the solver: its history from the 1999 TI-89 original to today, its complete logic in annotated pseudo-code — enough to build a simulator of your own — and worked exemplars, including one exam problem solved by the 2001 calculator and the 2026 port with the same answer, digit for digit.

    learn.symbulator.com/monograph.pdf

What it does

Four analyses, every element you meet in Circuits I and II.

Analyses
DC and AC as phasor analysis, transient in the time domain, and the complex frequency domain. Numerical circuits and, more to the point, symbolic ones.
Answers
Voltages at every node; current, voltage drop and power in every element. Real and complex power in AC, and the impedance each source sees looking back into the circuit.
Equivalents
Thévenin and Norton equivalents between any two nodes, and two-port parameters in six varieties.
Elements
Resistors, inductors, capacitors, mutual inductance, independent and dependent sources of both kinds, ideal operational amplifiers and ideal transformers.
Plots
Time-domain plots, and Bode gain and phase against frequency on a logarithmic axis.
Expert mode
Hand it the extra equations a problem gives you — a known current, a power to be delivered — and it solves for the component values you don't have. When the mathematics allows several solutions it returns them all, and a condition like vs > 0 picks the one you meant.

What it will not do

Symbulator simulates linear circuits, so there are no diodes and no transistors. It also will not help with problems that turn on applying a formula selectively rather than solving the circuit through.

And it is not a replacement for your brain. You have to understand circuit theory to use it. That has been the design's stance since the 2001 thesis: learn the manual techniques first, and let Symbulator verify what your own hand found.

On a calculator

Symbulator still runs on the calculators it grew up on.

Symbulator was born on the TI-89 in 1999 and took first place at the IEEE Region 9 student paper contest in 2000; versions 7 and 8 keep those calculators current.

  • 7

    TI-89 Titanium Stable

    Also the Voyage 200 and the classic TI-89. Transfer s7.tig to the calculator; Laplace transforms come from Lars Frederiksen's DiffEq alongside it.

    s7.tig DiffEq Documentation

  • 8

    TI-Nspire CX II CAS Beta

    Transfer s.tns and refresh the libraries. Still in beta, so expect the occasional bug.

    s.tns 300 solved problems Documentation

For developers

The engine underneath, if you want to build on it.

Not needed to use Symbulator — this is for people who want to call it from their own code, or fork it.

  • The Python package

    pip install symbulator — the core of Symbulator: the description parser, the stamping engine and the solver. It is what powers the app, exposed as a library you can import and call directly.

  • The source, on GitHub

    Both halves are there — the solver that does the algebra, and the interface that wraps it. Symbulator is now open source under the MIT licence, so ports and derivatives are welcome under the same licence, with attribution.