Create and analyze ALcad circuits#

Draw an analog or digital circuit, preserve editable files and choose the analysis supported by the current host.

Start an editable circuit#

  1. Open Schematic and choose New analog circuit or New digital circuit.

  2. Choose a component from the library, then click the canvas to place it. Escape cancels placement.

  3. Select a component and edit its reference, position, rotation and electrical parameters in Properties.

  4. Click two pins to connect them. A geometric crossing does not join nets.

  5. Use undo/redo to review edits, then choose Download circuit to keep an editable .alcad-circuit.json copy.

The independent circuit editor is different from a read-only DDS Digital Schematic import and from a native PCB project. Analog values use SI units: Ω, F, H, V, A and Hz. Digital buses support 1–64 bits; clocks use one bit. Schematic coordinates are grid coordinates rather than board millimeters.

Choose an analysis#

Analysis

Input and result

DC operating point

Resistors, independent DC voltage/current sources and ground; node voltages, signed branch currents and residuals.

Linear RLC AC / step

Supported R/L/C and independent sources; frequency response or zero-state step response with selected settings.

Digital simulation

Supported gates, buses, clocks and DFFs; four-state values 0, 1, X, Z over the sampled timeline.

SPICE netlist / schematic

Host-specific ngspice-backed analyses and explicitly supported devices/models; read the chosen runtime’s limits.

Choose a command only when the host reports it as available. Cloud RLC and digital calculations require their own current analysis capability; a DC permission does not enable every circuit solver. Native SPICE requires its configured runtime. Editing and netlist export can remain available without execution.

Check a simple analog result#

Begin with ground, a 5 V DC source and a 1,000 Ω resistor across it. Connect source pin 1 to the resistor and source pin 2 to ground; connect the resistor’s other pin to ground. Run DC operating point when available. Expect 5 V across the resistor and a current magnitude of 0.005 A. Current signs follow each element’s pin 1 → pin 2 direction.

For a saved .cir text-file exercise with exact expected tables, follow DDS SPICE DC. Do not add capacitors or transistors to an R/I/V-only DC exercise and assume the solver approximates them.

Read digital and RLC results#

For digital circuits, set input bit vectors and stimulus times before Run or Step. An initial DFF value of X is an unknown initial state, not necessarily a failed run. Read exact sampled bits and clock edges. The bounded circuit kernel does not simulate propagation delay, metastability or mixed-signal behavior.

For AC, read frequency, magnitude, phase and the selected source amplitude. A plotted magnitude is not automatically normalized gain. For transient steps, increase time resolution and compare convergence. Check units and residuals before accepting a curve.

Save, reopen and troubleshoot#

Download the editable circuit as well as result JSON/CSV when offered. Result files retain the executed input and its identity; ordinary circuit JSON does not necessarily include session stimulus settings. A browser draft is local to that origin/profile and is not a project backup. Edits, account/project changes and cancellation can invalidate displayed results.

Problem

Check

Floating or singular analog circuit

Ground connectivity, independent source constraints and supported elements.

Digital width/driver conflict

Equal net widths and at most one output driver per net.

Old curve disappears after editing

Run again on the saved/current document; retain prior exported evidence separately.

Import rejected

Use the format exported by the running version; keep the original file and current draft.