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Switch models

Voltage-threshold switch with a scalar control input Compare its models in the same order shown in the component inspector.

Symbol

Switch symbol
Default symbol for a new Switch component.

Model choice belongs to each placed Switch component. Changing one component does not change other instances or the default for future placements.

1

Ideal

Threshold-controlled switch with fixed 20 mΩ on resistance and 1 GΩ off resistance.

Default
Qualified analyses
  • Operating point
  • DC sweep
  • Transient

Model definition

Ideal is a stateful voltage-controlled connection. The switch turns on at the upper threshold and turns off at the lower threshold, preventing chatter inside the hysteresis band.

The closed and open states use fixed finite resistances for stable simulation.

Equations

Von=Vth+VH2,Voff=Vth−VH2V_{\mathrm{on}}=V_{\mathrm{th}}+\frac{V_H}{2},\qquad V_{\mathrm{off}}=V_{\mathrm{th}}-\frac{V_H}{2}
The Hysteresis field is the total separation between the two switching thresholds.
q+={1Vc≥Von0Vc≤VoffqVoff<Vc<Vonq^+=\begin{cases}1&V_c\geq V_{\mathrm{on}}\\0&V_c\leq V_{\mathrm{off}}\\q&V_{\mathrm{off}}<V_c<V_{\mathrm{on}}\end{cases}
The stored state q changes only after the control voltage crosses the appropriate threshold.
Rstate={20 mΩon1 GΩoffR_{\mathrm{state}}=\begin{cases}20\,\mathrm{m}\Omega&\text{on}\\1\,\mathrm{G}\Omega&\text{off}\end{cases}
Fixed finite resistances keep the ideal on and off states numerically stable.
VAB=RstateIABV_{AB}=R_{\mathrm{state}}I_{AB}
The switched terminal path is purely resistive in either state.

Parameters

ParameterDefaultAccepted values
ThresholdControl voltage at the center of the switching band.2.5 VAny finite value
HysteresisControl-voltage hysteresis band width.100 mVAt least 0

Limits

  • The 20 mΩ on resistance is numerical regularization, not a precision loss model.
  • No switching energy, output capacitance, reverse path, or hidden snubber is included.
  • AC sweep is not qualified.
2

Resistive

Adjustable on resistance with a fixed 1 GΩ off resistance.

Qualified analyses
  • Operating point
  • DC sweep
  • Transient

Model definition

Resistive uses the same stateful threshold and hysteresis behavior as Ideal, but the on resistance is an explicit engineering parameter.

The open state remains a fixed 1 GΩ resistance.

Equations

Von=Vth+VH2,Voff=Vth−VH2V_{\mathrm{on}}=V_{\mathrm{th}}+\frac{V_H}{2},\qquad V_{\mathrm{off}}=V_{\mathrm{th}}-\frac{V_H}{2}
The control input follows the same two-threshold state machine.
q+={1Vc≥Von0Vc≤VoffqVoff<Vc<Vonq^+=\begin{cases}1&V_c\geq V_{\mathrm{on}}\\0&V_c\leq V_{\mathrm{off}}\\q&V_{\mathrm{off}}<V_c<V_{\mathrm{on}}\end{cases}
State retention inside the hysteresis band is identical to the Ideal model.
Rstate={Ronq=11 GΩq=0,VAB=RstateIABR_{\mathrm{state}}=\begin{cases}R_{\mathrm{on}}&q=1\\1\,\mathrm{G}\Omega&q=0\end{cases},\qquad V_{AB}=R_{\mathrm{state}}I_{AB}
The selected on resistance replaces the Ideal model’s fixed 20 mΩ value; the off resistance remains fixed.

Parameters

ParameterDefaultAccepted values
ThresholdControl voltage at the center of the switching band.2.5 VAny finite value
HysteresisControl-voltage hysteresis band width.100 mVAt least 0
On resistanceClosed-state series resistance.100 mΩGreater than 0

Limits

  • Off-state leakage is fixed by the 1 GΩ open resistance.
  • Switching energy, capacitance, reverse conduction, and snubber behavior are omitted.
  • AC sweep is not qualified.
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