(R) Resistor Statement

Resistors in PLECS Spice support temperature dependence and variable resistance based on expressions. Unlike fixed PLECS resistor blocks, SPICE resistors can model temperature effects and semiconductor resistor geometries.

Linear Resistor

* Simple temperature-dependent resistor
Rname pos neg resistance <TC1=tc1> <TC2=tc2> <TEMP=temp> <M=m>

* Resistor with a model definition
Rname pos neg modelName <resistance> <L=l> <W=w> <TC1=tc1> <TC2=tc2> <TEMP=temp> <M=m>
.MODEL modelName R <NAME=value ...>

* Simple temperature-dependent resistor
Rname pos neg resistance <TC=tc1<,tc2>> <TEMP=temp> <M=m>

* Resistor with a model definition
Rname pos neg <resistance> modelName <L=l> <W=w> <TC=tc1<,tc2>> <TEMP=temp> <M=m>
.MODEL modelName R <NAME=value ...>

The TC instance parameter is followed by one or two temperature coefficients. Internally, we map these values onto TC1 and TC2.

  • The device type R must be specified in the model statement.

  • The inductance can also be set as the model parameter RES. If it’s defined in both the model and the instance, the instance value is used.

  • You can customize this model by providing a list of model parameter (name-value format) at the end of the .MODEL statement.

Instance Parameters

Parameter

Description

Default Value

TC1

Temperature coefficient for RES (first order correction)

\(0\,^\circ\text{C}^{-1}\)

TC2

Temperature coefficient for RES (second order correction)

\(0\,^\circ\text{C}^{-2}\)

TEMP

Device temperature

\(27\,^\circ\text{C}\)

L

Length of the semiconductor resistor

\(0\, \text{m}\)

W

Width of the semiconductor resistor

DEFW

M

Number of parallel devices

\(1\)

  • The default value for L is not permitted. Thus, a nonzero value must be set either in the instance statement or as a model parameter.

Model Parameters

Parameter

Description

Default Value

T_ABS

Device temperature

\(27\,^\circ\text{C}\)

RES

Resistance

\(0\, \Omega\)

RSH

Sheet resistance

\(0\, \Omega/\text{sq.}\)

DEFW

Default width of the semiconductor resistor

\(10^{-6}\, \text{m}\)

NARROW

Narrowing due to the etching process

\(0\, \text{m}\)

  • You can specify the instance parameters TC1, TC2, L, and W as model parameters too. If both are provided, the instance values take priority.

  • The instance parameter TEMP overwrites the model parameter T_ABS.

  • When the resistance is specified either in the instance statement or through the parameter RES, the parameters L, W, RSH, DEFW, and NARROW are ignored.

  • Both RES and RSH are temperature-corrected using TC1 and TC2.

  • The default value for RSH is not permitted and a nonzero value must be chosen.

Variable Resistor

Rname pos neg R={function body}

Rname pos neg R=function body

  • If exactly one = is included, everything to the right of = is treated as function body.

Warning

The variable resistor is implemented as a current source with a user-defined function. Hence, the resistance function must never evaluate to zero.

Examples

Rg 1 2 4.7 TC1=0.001 TEMP=90

Vctrl ctrl 0 PULSE 0 1 0 1e-6 1e-6 0.5 1
Rload out 0 R={10+5*V(ctrl)}