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