Simulator Reference: Resistor

Netlist Entry

Rxxxx n1 n2 [model_name] [value] [L=length] [W=width] [ACRES=ac_resistance]
[TEMP=local_temp] [TC1=tc1] [TC2=tc2] [M=mult] [DTEMP=dtemp]

n1	Node 1
n2	Node 2
model_name	(Optional) Name of model. Must begin with a letter but can contain any character except whitespace and '.'
value	Resistance (W)
length	Length of resistive element in metres. Only used if value is omitted. See notes below
width	Width of resistive element in metres. Only used if value is omitted. See notes below
ac_resistance	Resistance used for AC analyses and for the calculation of thermal noise. If omitted, value defaults to final resistance value.
local_temp	Resistor temperature (C)
tc1	First order temperature coefficient
tc2	Second order temperature coefficient
mult	Device multiplier. Equivalent to putting mult devices in parallel.
dtemp	Differential temperature. Similar to local_temp but is specified relative to circuit temperature. If both TEMP and DTEMP are specified, TEMP takes precedence.

Notes

If model_name is omitted, value must be specified.
If model_name is present and value is omitted, length and width must be specified in which case the value of the resistance is RES * RSH * L/W where RSH is the sheet resistance model parameter and RES is the resistance multiplier. See model parameters below. If ACRES is specified and non-zero its value will be used unconditionally for AC analyses and the calculation of thermal noise.

Resistor Model Syntax

.model modelname R ( parameters )

Resistor Model Parameters

Name	Description	Units	Default
RES	Resistance multiplier		1
TC1	First order temperature coefficient	1/° C	0
TC2	Second order temperature coefficient	1/° C²	0
RSH	Sheet resistance	Ω/sq	0
KF	Flicker noise coefficient	m²/Ω²	0
EF	Flicker noise exponent		1
TNOM, T_MEASURED	Reference temperature; the temperature at which the model parameters were measured	° C	27
T_ABS	If specified, defines the absolute model temperature overriding the global temperature defined using .TEMP	° C	.TEMP
T_REL_GLOBAL	Offsets global temperature defined using .TEMP. Overridden by T_ABS	° C	0.0

Notes

The flicker noise parameters are proprietary to SIMetrix. Flicker noise voltage is: \[ V_n^2 = \text{KF} \cdot \text{RSH}^2/(L\cdot W) \cdot V_r^2 \cdot \Delta f/f^{\text{EF}} \]

Where:

???MATH???Vr???MATH??? = Voltage across resistor.

The equation has been formulated so that KF is constant for a given resistive material.

If one of L, W is not specified, the flicker noise voltage becomes:

\[ V_n^2 = \text{KF} \cdot \text{R}^2 \cdot V_r^2 \cdot \Delta f/f^{\text{EF}} \]

Where R is the final resistance.

i.e. the noise current is independent of resistance. This doesn't have any particular basis in physical laws and is implemented this way simply for convenience. When resistor dimensions and resistivity are unavailable, the value of KF will need to be extracted for each individual value.