Voltage controlled switch


Sxxxxxxx (n+ n- nc+ nc-) modelname ic

Model (required):

.model modelname SW args
Current controlled switch


Wxxxxxxx (n+ n- ce) modelname ic

Model (required):

.model modelname CSW args


Voltage or current controlled switch.


N+ and n- are the positive and negative element nodes, respectively.

For voltage controlled switch, Nc+ and nc- are the controlling nodes.

For current controlled switch, ce is the name of a controlling element.

Modelname is the model name.

A switch is a resistor between n+ and n-. The value of the resistor is determined by the state of the switch.

control resistance
vc > von
ic > ion
vc < voff
ic < ioff
otherwise no change

You may specify ON or OFF to indicate the initial state of the switch when the controlling voltage is in the hysteresis region.

The parameters ron and roff must have finite positive values.

Model Parameters

Voltage controlled switch
vt Threshold voltage. (Default = 0.)
vh Hysteresis voltage. (Default = 0.)
von On control voltage. (Default = vt + vh)
voff Off control voltage. (Default = vt - vh)
ron On resistance. (Default = 1.)
roff Off resistance. (Default = 1e12)
Current controlled switch
it Threshold current. (Default = 0.)
ih Hysteresis current. (Default = 0.)
ion On control current. (Default = it + ih)
ioff Off control current. (Default = it - ih)
ron On resistance. (Default = 1.)
roff Off resistance. (Default = 1e12)

Time step control

A change of state is considered to be an analog event. An input crossing a threshold is a “cross event”. Cross events will generate extra time steps so the switch timing is accurate.

A switch can be used anywhere in a circuit to improve timing accuracy by sensing cross events.

Switches also influence time step control as resistors, which control smoothness by curve fitting.


Switches are linear devices that do not iterate unless there is a state change.

gnucap/manual/devices/switches.txt · Last modified: 2015/12/11 15:39 (external edit)
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