RFspice – Online SPICE Circuit Simulator with Schematic Capture

SCHEMATIC1 generated

SPICE netlist

Import or select a model file.

XY plot builder

X results X quantity / expression X unitsInto plot Y results Y quantity / expression Y unitsY axis Style

Choose any result for X, then any compatible result for Y. Quantity names are unitless; choose display units separately. Smith uses the raw complex Y quantity (normally S11/S22) and ignores the Y-units/axis controls. Destinations are explicit Rn,Cn cells. In multi-plot layouts, drag a plot by its small Rn,Cn handle to swap/rearrange displays.

Displays

Data browser

Click a quantity to load it as Y in the XY builder. Shift-click loads it as X.

Expressions & templates

0 named

Expression help · editor, waveform + Measurements cookbook (20 examples)

One expression system: NAME = equation creates a reusable named result. Waveform results appear under Derived signals; scalar reductions appear under Measurements. Scalar names may depend on earlier named results.

Templates: open Expressions…. A template only inserts visible, editable equations. It may optionally pre-fill one plot, but every X, Y, unit, axis and style remains editable in the XY builder.

Signals: v(out), i(vsup), i(@r1[i]), bare node names, or "any name". Differential: v(a,b). Constants: pi e j; x-axis: time/frequency; suffixes: 1k 10u 2meg.

Waveform windows: rmswin(x,window), avgwin(x,window). Scalar range reducers: rmsrange, avgrange, minrange, maxrange, peakabsrange, pkpkrange, integralrange. Exact-tone scalar extraction: ampat, rmsat, phaseat, wattsat, dbmat. Other functions:

VOUT_RMS = rmsrange(v(out),5u,10u)
VOUT_AVG = avgrange(v(out),5u,10u)
VOUT_PK = peakabsrange(v(out),5u,10u)
VOUT_PP = pkpkrange(v(out),5u,10u)
POUT_W = VOUT_RMS^2/50
POUT_DBM = 10*log10(POUT_W/1m)
PENV_W = rmswin(v(out),71.43n)^2/50
PENV_DBM = 10*log10(max(PENV_W,1e-15)/1m)
PDC_INST_W = -v(vdd)*i(vsup)
PDC_W = abs(avgrange(v(vdd)*i(vsup),5u,10u))
PIN_W = abs(avgrange(v(in)*i(vin),5u,10u))
GAIN_DB = 10*log10(POUT_W/max(PIN_W,1e-15))
EFF_PCT = 100*POUT_W/max(PDC_W,1e-15)
PAE_PCT = 100*(POUT_W-PIN_W)/max(PDC_W,1e-15)
PDC_ENV_W = abs(avgwin(v(vdd)*i(vsup),71.43n))
EFF_ENV_PCT = 100*PENV_W/max(PDC_ENV_W,1e-15)
VDIFF = v(outp,outn)
S21_DB = db("S_2_1")
S11_RL_DB = rl("S_1_1")
ZIN_OHM = zmag("S_1_1",50)

FFT dataset

Signal Window Points StartStop Remove DC

S-parameter setup

Start Stop Step Mixed pairs

This section only defines/runs the S-parameter dataset. It does not create a display. Plot frequency, S-parameters and derived Expressions with the XY builder.

Temperature sweep setup

Start (°C)Stop (°C)Explicit temperatures (optional; overrides range)Step (°C)Sample frequency Linear analysis Custom commands Drive / noise sourceSecond tone sourceTone 1Tone 2Input per tone (dBm)Reference Z (Ω) Input expressionOutput / noise voltageSamples / cycleSettle cyclesMeasure cyclesBeat cycles

Measurements: name, unit, analysis, expression. TwoTone rows enable a two-tone test at every temperature. For transient vectors use scalar measurements such as rms() or avg(). AC/noise vectors are sampled at the chosen frequency.

Results appear as Temperature Sweep in XY Plot Builder. Normal analyses keep their own temperature.

Nonlinear sweep setup

Mode Source 1Source 2 f1f2 Amplitude startAmplitude stop StepsScale Input signal Output signal Reference Z (Ω)Samples / cycle Settle cyclesMeasure cycles Minimum beat cycles

This section only defines and runs the sweep. It does not create a display. Results are published to one Nonlinear RF result store for arbitrary X/Y plotting.

Run a simulation, then click signals on the left (or type an expression).
Drag = box zoom · wheel = zoom X · Ctrl+wheel = zoom Y · Shift/right-drag = pan · edit axis endpoint values for exact limits · double-click an endpoint for Auto

Traces

Measurements

Statistics ·

Markers

ngspice console

RFspice – online SPICE circuit simulator