3.18  R: Resistor

3.18.1  Syntax


Rxxxxxxx n+ n– value
Rxxxxxxx n+ n– expression
Rxxxxxxx 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.


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:
  1. A simple value. This is the resistance in Ohms.

  2. 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.

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

  4. 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)

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.