Part 1

What Symbulator is

A symbolic solver for linear circuits. What it does, what it refuses, and the nine things a circuits course covers that it will not.

Part 2

The circuit description

All fifteen element letters with their fields, the naming rules, node 0, brackets, and the SI prefix shorthand. The densest page here, and the one to come back to.

Part 3

Running it, and reading the answer

One run returns every answer in the circuit. The names they come back under, what each one means, and the two spellings of any of them.

Part 4

Symbols, Define and Expert Mode

Any value may be a symbol, and the answer comes back in terms of it. Define supplies values; Expert Mode adds equations, unknowns and conditions to the system.

Part 5

Sources, conductances and shorthands

Current sources, dependent sources of all four kinds, conductance as a value, and the parallel-resistor shorthand.

Part 6

Equivalents and the load question

Equivalent resistance, Thévenin and Norton at a pair of nodes, and the load answers that come with them.

Part 7

Operational amplifiers

The o element is an ideal op amp — a nullor. What that buys you, what it hides, and how to model a real one when the ideal answer is not enough.

Part 8

Capacitors, inductors and TR

Storage elements, initial conditions in the fifth field, transient analysis, switched circuits as two runs, and plotting an answer against time.

Part 9

AC, phasors and power

Sinusoidal steady state at one ω, rectangular or polar, and the four power answers — including the one setting that changes an answer rather than its appearance.

Part 10

Mutual inductance and transformers

m couples two named inductors and the node order carries the dots. t is an ideal transformer, two-terminal or four.

Part 11

The s-domain, transfer functions and plots

FD returns answers in s, which is where transfer functions come from. The t2s and s2t shortcuts, and all four plot types.

Part 12

Two-ports

Six parameter sets out of any network, the same six letters as circuit elements, and the gain tool.

Part 13

The rest of the toolbox

By-Hand Equations, the Numerical Solver, the SPICE Translator, the schematic, and the solver as a Python package.

Part 14

Reference

Every element, every answer name, what each tool returns, every setting, and what a saved file remembers. Lookup, not reading.

Who made this

Symbulator is the work of one person, shaped by the feedback of many. Created in 1999, MIT-licensed since 2026. See the Course for full credits.