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 and Bode 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 7, released in 2023, is written — like all its predecessors — for Texas Instruments' TI-89 Titanium, and runs on all compatible devices, such as the Voyage 200 and the classic TI-89. There is a version for the TI-Nspire CX II CAS called version 8, 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 latest version of Symbulator for the TI-89 platform is version 7 (date stamp 08 July 2023). We believe it is free of bugs; if any is found we will revise and reupload, updating the date stamp. It runs on the TI-89 Titanium and the Voyage 200.

To get Symbulator 7, download this file: s7.tig, which you will transfer to your calculator.

DiffEq

Since the CAS in the TI-89 Titanium does not do Laplace transforms, Symbulator relies for that on a software called DiffEq, made by my friend Lars Frederiksen.

To get DiffEq, download this file: diffeq.zip. From that zip file you need to extract a file called diff206.89g, which you then transfer to your calculator.

Install

Given the way TI-89 calculators work, programs run faster once they have been executed at least once and then archived. We call that 'installing' them. Both Symbulator and DiffEq have installation programs, which you run in your calculator as follows:

s\install()
Archive s\install

and

dif\install()
Archive dif\install

That is all the software you need!

Where to symbulate

After years of using Symbulator, I have developed certain best practices that I share as Tips in this documentation. The first: always make MAIN your current folder before running a simulation, and empty MAIN of spurious variables before each one.