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Tektronix
Spirals
20%
Volts/Div
Time/Div
01

Write

* RC Low-Pass Filter
V1 in 0 PULSE(0 5 0 1n 1n 0.5m 1m)
R1 in out 10k
C1 out 0 100n
.tran 10u 5m

SPICE netlists with syntax highlighting and autocomplete

02

Simulate

ngspice 43

Circuit: RC Low-Pass Filter

Doing transient analysis...

501 data points, 23ms

complete

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03

Schematic

R1 10k R2 4.7k Vin Vout

Auto-generated circuit diagrams with color-coded resistors

04

Visualize

Interactive waveforms + oscilloscope mode

Resistor Color Codes Learn to read 4-band color codes
mcltspice MCP Server 37 tools · Linux & macOS
Forrest Mims Mini-Notebooks 15 classic hand-drawn electronics guides

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28 notebooks available

Timers & Oscillators(4)

Op-Amp Circuits(3)

Sensors & Measurement(1)

Communications & RF(1)

Amplifiers(1)

Passive & Beginner(2)

Advanced Topics(16)

V11R015.9kC010nV21E1100000R1a15kR1b15kC1a10nC1b11.7nX1IDEALOAR2a6.2kR2b6.2kC2a10nC2b68.3nX2IDEALOAin1rc_outin2a1b1s1outa2b2s2outout

4th-Order Sallen-Key Butterworth Filter

ngspice

Passive RC filters roll off at a gentle -20 dB/decade. For serious filtering -- anti-aliasing before an ADC, crossover networks in audio, sensor signal conditioning, biomedical instrumentation -- you

5 cellsMar 7, 2026
Vin0.2C110uQ1NPN1Rb1100kRb2100kCe1100uD2DBIASQ3PNP1Re11kD1DBIASCout470uQ2NPN1Rc14.7kRload8inpbasecolem1VCC 12VEE -12dmidoutq2bspk

Class AB Push-Pull Audio Amplifier

ngspice

The output stage of nearly every analog audio amplifier ever built. From vintage hi-fi receivers to guitar amps to PA systems, the complementary push-pull topology drives speakers efficiently while ke

6 cellsMar 7, 2026
Vdd5D1SCHOTTKYC1100nVclk1PULSEvdd

Dickson Charge Pump Voltage Multiplier

ngspice

Need 15V from a 5V supply but have no room for an inductor? The Dickson charge pump generates high voltage from low voltage using only capacitors and diodes -- no magnetics, no transformers. Used in E

5 cellsMar 7, 2026

DK25 LLC Converter Optimized

ngspice

LLC resonant converter targeting 390V, 180V, 24V rails - optimized inductor values

2 cellsApr 4, 2026
SYMATTR10n 10n 4.8u 10u)ValuePULSE(0

DK25 Power Supply LLC Converter

ngspice

LLC resonant converter targeting 390V, 180V, and 24V DC rails

2 cellsApr 7, 2026
SYMATTR10n 10n 4.8u 10u)ValuePULSE(0

DK25 Power Supply LLC Converter

ngspice

LLC resonant converter with coupled inductors - targets 390V, 180V, 24V rails

2 cellsApr 7, 2026
Vin12S1IDEAL_SWL14.7uS2IDEAL_SWVpwmPULSEResr10mBinvV = 5 - V(pwm)C147uRload1supplyswlxoutpwmlsd

Synchronous Buck Converter

ngspice

Every phone charger, laptop regulator, server VRM, and EV power module uses a buck converter. It is THE circuit of modern power electronics -- converting a higher DC voltage to a lower one with 90%+ e

4 cellsMar 6, 2026

Timbre Sim 2: Switch-Level SC Biquad Self-Oscillation

ngspice

Switch-level model of the SC biquad self-oscillator from Sim 1, replacing continuous-time equivalent resistors with actual voltage-controlled switches and two-phase non-overlapping clock (500 kHz). De

2 cellsMar 8, 2026
timbreswitched-capacitorself-oscillationswitch-levelbiquadpsoc

Timbre Sim 3: Relaxation Oscillator Mode

ngspice

Triangle/square wave relaxation oscillator using SC integrator + CT Schmitt trigger comparator. Demonstrates the second oscillation mode available in the CY8C29466's analog fabric. Uses only 2 of 12 a

2 cellsMar 8, 2026
timbrerelaxation-oscillatortriangle-wavesquare-waveswitched-capacitorpsoc

Timbre Sim 4: Mid-Note Topology Switching

ngspice

Core patent claim demonstration: audio-rate topology reconfiguration. A sustained biquad self-oscillation at 1592 Hz transitions to relaxation oscillation at 1139 Hz mid-note via behavioral conductanc

2 cellsMar 8, 2026
timbretopology-switchingreconfigurationpatent-claimswitched-capacitor
V_phi1PULSEC_par_fb150fC_par_in150fC_par_r2150fS_fb1SWS_in1SWS_r2_1SWC_par_fb250fC_sw_fb20pS_fb2SWC_par_in250fC_sw_in20pS_in2SWC_par_r2250fC_sw_r220pS_r2_2SWR410kXU3opamp_bVinPULSEC11nC_ac10uG_Q2uR_sk12.7kRdc110MegXU1opamp_bV_phi2PULSEC21nRdc210MegXU2opamp_bR310kR_ac10kC_sk12.2nR_sk22.7kC_sk21nXU4opamp_extR_fb_sk0.001B1V=12*tanhB1V=12*tanhphi1sw_fbsw_insw_r2lp_invinbpphi2sum1sum2buf_inac_outsk_midlpsk_inpfiltfilt_fbout

Timbre Sim 5: Clock Feedthrough Characterization & Output Filtering

ngspice

Quantifies the clock noise artifacts inherent to switched-capacitor synthesis and demonstrates the reconstruction filter: a 2nd-order Sallen-Key Butterworth LPF at 40 kHz. The raw SC biquad output (sw

2 cellsApr 7, 2026
timbreswitched-capacitorclock-feedthroughsallen-keyreconstruction-filterCY8C29466
VpulsePULSERdrv10L110nC14pL210nC24pL310nC34pL410nC44pL510nC54pL610nC64pL710nC74pL810nC84pL910nC94pL1010nC104pRload1meginpnearn1n2n3n4n5n6n7n8n9far

Transmission Line Signal Integrity

ngspice

Above 50 MHz, a wire is no longer just a wire. It becomes a transmission line with characteristic impedance, propagation delay, and reflections. This is THE single biggest cause of signal integrity fa

6 cellsMar 6, 2026

Untitled Notebook

ngspice

Add SPICE cells below to begin simulating.

1 cellMar 2, 2026

Untitled Notebook

ngspice

Add SPICE cells below to begin simulating.

1 cellMar 30, 2026
V1PULSEC_couple0.1pC_parasitic5prail

Wurlitzer 555 — AC Coupling Feasibility (Sim 1)

ngspice

Question: Does the organ's own TOD divider square wave produce a measurable signal at a pickup electrode near the contact rail? The Circuit The Wurlitzer 555's Top Octave Divider (TOD) chain produces

9 cellsMar 6, 2026
wurlitzer-555ac-couplingcapacitive-dividerorgan-midiapproach-b
V_railPULSEC_couple3pC_parasitic5pE_buffer1R_load10megB_rectV=abs(V(buf))R_env10kC_env100nrailpickuprectenvbuf

Wurlitzer 555 — Full Detection Chain (Sim 3)

ngspice

Context: Sim 1(https://spicebook.warehack.ing/notebook/wurlitzer-555-ac-coupling-feasibility-sim-1-64986777) confirmed that AC coupling produces measurable pickup voltage across the key travel range.

8 cellsMar 6, 2026
wurlitzer-555envelope-detectordetection-chainorgan-midiapproach-badcnoise-analysis