Analog Circuit Lab
Build a small ideal linear circuit by assigning each element two node numbers. The local modified-nodal solver reports the DC operating point, complex AC phasors at one selected frequency, and a backward-Euler transient after ideal sources step from zero to their DC values. Node 0 is ground; each element's positive current goes from its a terminal to b. Capacitor voltages and inductor currents start at zero for the transient. AC source entries are real, zero-phase peak phasors. This is a bounded teaching model, not electrical safety or physical hardware validation.
Key features
- Actual modified nodal analysis for R, C, L and independent V/I sources between any two listed nodes
- DC capacitor-open and inductor-short solution with explicit singular topology errors
- Single-frequency complex AC voltage and current magnitude/phase for zero-phase peak source phasors
- Backward-Euler RLC step transient with zero stored initial energy, 1–120 samples and cooperative cancellation
- Per-node and per-element results, waveform SVG, transient CSV, full report JSON and restorable circuit JSON
- Strict node, value and size bounds; no external simulation API, paid engine or uploaded circuit
How to use
- Use the RC example or choose 1–8 non-ground nodes. Node 0 is the reference ground; equal node numbers mean an electrical connection.
- Add 1–16 R, C, L, voltage or current elements. Set each a and b terminal to different nodes, enter SI values, and supply separate AC peak values for sources.
- Select the AC frequency and transient step size/sample count. Run to solve DC, AC and zero-energy step transient; stop a run with Cancel if needed.
- Inspect node voltage and a→b element-current tables plus the time waveform. An unsolved DC topology or contradictory ideal sources produces an explicit error.
- Download the SVG, CSV, report JSON or circuit JSON, then restore a saved circuit from a local file or pasted JSON.
Use cases
- Compare an RC low-pass DC output, AC attenuation and step charging
- Inspect RL inductor current as it rises toward its steady value
- Check Kirchhoff node currents in a small linear network
- Share a reproducible ideal circuit and analysis settings as a local JSON file
Frequently asked questions
Which components and circuit shapes are supported?
Ideal linear resistors, capacitors, inductors, independent voltage sources and current sources may connect between any two different numbered nodes, including ground. The model has at most 8 non-ground nodes and 16 elements. Diodes, transistors, dependent sources, nonlinear behavior and distributed lines are not modeled.
How are DC, AC and transient sources interpreted?
The value field is the signed DC value and the ideal step value after t=0. The AC field of a voltage or current source is a signed real, zero-phase peak phasor at the selected frequency. AC and DC solutions are separate; the transient starts with zero capacitor voltage and zero inductor current and is sampled from the first full time step.
Why does an apparently connected circuit report singular?
A floating node that has only a capacitor path has no DC reference because an ideal capacitor is open at DC. Conflicting ideal voltage constraints and some ideal-source loops also have no unique solution. The tool reports the failing DC, AC or transient mode instead of fabricating a value.
Is the step waveform an exact continuous-time solution?
No. It uses implicit backward-Euler integration at the selected fixed time step. Decrease the step and compare results to judge numerical change; it does not model parasitics, switch timing, tolerance, saturation or high-frequency layout effects.
What is the direction of a displayed branch current?
Positive current flows from the element's a terminal toward its b terminal. An AC cell shows peak magnitude and phase in degrees under the same direction convention.
Are circuit details sent to a server or safe for hardware design?
The analysis and downloads run in this browser tab without a circuit API upload. The ideal, bounded model does not check component ratings, shock/fire risk, insulation, grounding practice or real-world hardware suitability.
Privacy
Circuit values and simulation results stay in this browser tab. JSON, CSV and SVG files are downloaded only when you request them; circuit data is not submitted to an application API.
Comments & questions