## 3.18 `R`: Resistor

### 3.18.1 Syntax

#### Device

`R`*xxxxxxx n+ n– value*

`R`*xxxxxxx n+ n– expression*

`R`*xxxxxxx n+ n– model* {`L=`*length*}
{`W=`*width*} {`TEMP=`*temperature*}

`.resistor` *label n+ n– expression*
#### Model (optional)

`.model` *mname* `R` {*args*}

`.model` *mname* `TABLE` {*args*}
### 3.18.2 Purpose

Resistor, or general current controlled dissipative element.
### 3.18.3 Comments

*N+* and *n–* are the positive and negative element nodes,
respectively. *Value* is the resistance in Ohms.

The resistor (type `R`) differs from the admittance (type `Y`) in
that the resistor is a current controlled element, and the conductance is a
voltage controlled element, in addition to the obvious use of conductance
(1/*R*) instead of resistance.

You may specify the *value* in one of three forms:
- A simple value. This is the resistance in Ohms.

- An expression, as described in the behavioral modeling chapter. The
expression can specify the voltage as a function of current, or the
resistance as a function of time.

- A
*model*, as described in the behavioral modeling chapter. The
`table` model describes a table of voltage vs. current.

- A
*model*, which calculates the resistance as a function of length
and width, referencing a `.model` statement of type `R`. This
is compatible with the Spice-3 “semiconductor resistor”.

### 3.18.4 R Model statement

A model statement may be used,, with model type `R` or `Res`.
The parameters are:
`RSH` = *x*- Sheet resistance. (Ohms / square). (Required)

`CJSW` = *x*- Junction sidewall capacitance. (Farads /
meter). (Default = 0.)

`DEFW` = *x*- Default width. (meters). (Default = 1e-6)

`NARROW` = *x*- Narrowing due to side etching. (meters).
(Default = 0.)

`TC1` = *x*- First order temperature coefficient.
(Farads / degree C). (Default = 0.)

`TC2` = *x*- Second order temperature coefficient.
(Farads / degree C squared). (Default = 0.)

`TNOM` = *x*- Parameter measurement temperature.
(degrees C.). (Default = 27.)

Resistance is computed by the formula:
resistance = RSH * (L - NARROW) / (W - NARROW)

After the nominal value is calculated, it is adjusted for temperature
by the formula:
value *= (1 + TC1 * (T-T0) + TC2 * (T-T0)^2)

### 3.18.5 Probes

The standard probes for all basic elements are all available. See the
`print` command for documentation.