A starting point, not a blank page
Circuits you can take apart.
Open a demo, inspect its connections and change its values. Each example is an editable project, ready for your experiments.
RC low-pass filter
A 1 kΩ / 1 µF filter. Compare the input and output; sweep AC to find the 159 Hz corner.
FundamentalsVoltage divider
Two equal resistors divide a 5 V source to 2.5 V. Use the multimeter to measure each node.
SemiconductorsLED current limiter
A 5 V supply, a 330 Ω series resistor, and a generic red LED.
FundamentalsRC step response
Charge a 10 µF capacitor through 1 kΩ. Enable zero initial conditions to see the 10 ms time constant.
FiltersRLC resonance
A series RLC circuit. The LC resonance is approximately 1.59 kHz.
SemiconductorsHalf-wave rectifier
Rectify a 50 Hz sine into a resistive load.
DigitalLogic playground
Two different clocks drive an XOR gate. Inspect their truth states on the logic analyzer.
DigitalDivide-by-two flip-flop
Connect inverted Q back to D and clock a D flip-flop to divide frequency by two.
Timers555 astable oscillator
A complete 555 oscillator with timing resistors, timing and control capacitors, reset wiring and an output load. Approximately 48 Hz.
PowerRegulated bridge supply
Full-wave bridge rectification, reservoir capacitor and a 5 V regulator feeding a 1 kΩ load. Educational models; no transformer or mains connection.
Digital8-bit counter
An enabled eight-bit counter driven by a 100 Hz clock. Inspect the successive divide-by-two outputs on the logic analyzer.
Digital4-bit arithmetic unit
Add two four-bit counters with carry. This larger digital circuit demonstrates buses built from individual nets and a fourteen-terminal adder.
PCB designVoltage divider · routed PCB
A complete schematic and routed 70 × 50 mm board with two resistors and a three-pin connector. Switch to PCB layout to inspect or export it.
VerificationRC filter · tolerance verification
A reproducible filter design check: R ±5%, C ±10%, all four corners. Open Verification and run the study; require the −3 dB crossing to stay within 130–200 Hz. Select ngspice to compare engines.
VerificationResistor noise · temperature study
Two 1 kΩ resistors, 1 Hz–100 kHz bandwidth. Run −40 / 27 / 85 °C with ngspice; expect 0.802 / 0.910 / 0.994 µV RMS output noise. Input-referred noise is twice the output.
VerificationDiode bias · temperature study
A physical numeric diode card biased through 1 kΩ from 5 V. Compare forward voltage at −20 / 27 / 85 °C in ngspice; it decreases as temperature rises. Inspect the model and captured netlists.
AmplifiersNon-inverting amplifier · gain check
A ±12 V behavioral amplifier, 100 mV input and 90 kΩ / 10 kΩ feedback. Run all four 1% resistor corners and verify 0.97–1.03 V output. This model has no physical bandwidth or noise model.
PCB designVoltage divider · two-layer via routing
A routed divider with two through vias and a bottom-copper segment. Run DRC, inspect both layers, and export the manufacturing ZIP. Generic footprint mappings require review before fabrication.