KiCad SPICE Simulation Tutorial

Resources

• KiCad Simulation Documentation: docs.kicad.org — Spice Simulation Guide
• ngspice Engine Manual: ngspice.sourceforge.io — User Documentation
• KiCad Community Forum: forum.kicad.info — Simulation Tips & Tricks
• KiCAD Video Tutorial (slightly dated): https://www.youtube.com/watch?v=3_XpWt_rTaU

1. Build the Circuit Layout

KiCAD RC Circuit

• Open KiCad Schematic Editor.
• Press A to open the Symbol Chooser and place the following components:
  • Resistor ($R$): Generic resistor symbol.
  • Capacitor ($C$): Generic capacitor symbol.
  • Power / Voltage Source: Search for VPULSE or VSIN in the Simulation_SPICE library.
  • Ground: Press P or search for GND.
• Wire the components into an RC low-pass configuration (Voltage Source $\rightarrow$ Resistor $\rightarrow$ Capacitor to Ground).
• Press L to add Net Labels to your key signal lines:
  • Label the node between the source and resistor as in.
  • Label the node between the resistor and capacitor as out.

2. Configure Component Values and SPICE Models

• Double-click the Resistor and set its value to 31k.
• Double-click the Capacitor and set its value to 0.1uf (or 100n).
• Double-click the VPULSE source to assign its excitation properties:
  • Via Parameter Window: Right-click the component $\rightarrow$ Properties $\rightarrow$ Simulation Model $\rightarrow$ Select Source tab $\rightarrow$ Choose Pulse.
  • Key Settings for a 5 kHz Pulse:
    • Initial value ($V_1$): 0
    • Pulsed value ($V_2$): 5
    • Period ($PER$): 200u ($1 / 5\text{ kHz}$)
    • Pulse width ($PW$): 100u ($50%$ duty cycle)
    • Rise/Fall time ($TR$/$TF$): 1n

3. Configure and Run the Simulation

• From the top menu, go to Inspect $\rightarrow$ Simulator.
• Click Simulate $\rightarrow$ Setup (or the gear icon) to choose your analysis type:

Transient Analysis (Time-Domain Waveforms)

• Select the TRAN — Transient Analysis tab.
• Time step: 10u (captures fine waveform details).
• Final time: 2m (runs for 2 milliseconds to display 10 full cycles).
• Click OK, then click the green Run Simulation button.

AC Sweep (Frequency Response / Bode Plot)

• Select the AC — Small-Signal Analysis tab.
• Variation: Decade
• Number of points: 100
• Start frequency: 1 (1 Hz)
• Stop frequency: 100k (100 kHz)

4. Plot and Measure Waveforms

• In the right-hand panel under Signals, check the boxes next to the nodes you want to display:
  • Check V(in) to view the input signal.
  • Check V(out) to view the filtered output signal.
• Use the built-in measurement tools:
  • Check Cursor 1 next to a signal name to enable an interactive measurement cursor on the graph.
  • Drag the cursor line across the plot to measure exact peak voltages, DC offset, or rise times.