Introduction

What is Symbulator

Symbulator is a program to solve linear electric circuits symbolically and numerically in a calculator. It takes numerical and symbolic values, and returns numerical and symbolic results. The odd-sounding name is a portmanteau of "symbolic simulator". Symbulator is widely regarded as the best symbolic simulator of linear electric circuits ever made for a calculator.

What analyses can it do?

Symbulator can solve circuits using four types of analysis: direct current (DC), alternating current (AC), transient time-domain (TR), and complex frequency-domain (FD). It analyses numerical and, more importantly, symbolic linear circuits, returning the voltages in all nodes and the currents, voltage drops and power in all elements. It also finds the passive, Thévenin / Norton and two-port equivalent of a circuit, and draws time domain plots.

What elements does it accept?

Symbulator accepts elements such as resistors, inductors, mutual inductance, capacitors, independent and dependent current and voltage sources, ideal operational amplifiers, ideal transformers and six types of two-ports.

Where does it run?

Symbulator 8, released in 2023, is adapted to run on the TI-Nspire CX II CAS calculator by Texas Instruments. There is also a version for the TI-89 Titanium called version 7, and a newer Python/SymPy port called version 9.

Why use Symbulator?

Symbulator is extremely useful on the circuit theory problems engineering students face in Circuits I and II. It lets the student focus on understanding circuit analysis rather than on the mathematics of solving it.

Strengths

• A fantastic tool to solve circuits composed of ideal, linear elements.
• Shines in solving circuits with symbolic values, and symbolic results.
• Offers the absolute simplest way to define dependent sources.
• Includes ideal transformers and six different two-ports.

Limitations

• Does not simulate non-linear elements, such as diodes and transistors.
• Will not answer under-defined problems that rely on applying formulas selectively rather than solving a circuit completely.
• Is not a replacement for your brain or an excuse to not study. You must understand circuit theory to use it.

Symbulator is free!

Symbulator has always been free of cost, and always will be. (You are welcome!)

Since 2026, Symbulator is also open source under the MIT licence. You are free to use it, change it and port it to other platforms; all the licence asks is that the copyright notice and the attribution to the original author travel with it.

Download

Symbulator

The version of Symbulator for the TI-Nspire CX II CAS is called version 8 beta (date stamp 08 July 2023). It may still contain the occasional bug; as bugs are found and fixed, we will revise and reupload, updating the date stamp.

To get Symbulator 8, download this file: s.tns, transfer it to your calculator, and refresh the libraries.

Laplace Functions

Since the CAS in the TI-Nspire CX II CAS does not do Laplace transforms, Symbulator relies for this on another software, which I call Laplace Functions.

This software was made, around the same time Symbulator was being created, by my friend Lars Frederiksen, one of the most gifted programmers for TI-Basic ever. Lars made two programs for the TI-92+/Voyage and the TI-89: one he called DiffEq, because it also solves differential equations, and the other Advanced Laplace, which packed improved versions of his Laplace functions.

The latter was automatically adapted for the TI-Nspire by Philippe Fortin, who renamed the group of functions ETS_specfunc. Not being a fan of that name, and given my friendship and collaboration with Lars, I have taken the liberty of renaming the file here to LF, which in my eyes stands both for Laplace Functions and for Lars Frederiksen.

Download lf.tns, transfer it to your calculator, and refresh the libraries.

Solved problems

I have solved all the problems in this documentation, each in a separate TI-Nspire document. This zip file, problems.zip, contains three hundred solved problems.

Before you start

Clean slate

Before running a simulation in the Nspire, either create a new document or delete from the current one every variable unrelated to your simulation.

And if a simulation fails or aborts and leaves variables behind, move to a new document or delete them before running it again.