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Resistors

General Form:
rname n1 n2 [value | modname] [r=expr] [temp=temp [tc1=tcoeff1] [tc2=tcoeff2]
[l=length] [w=width] [noise=mult]
rname n1 n2 poly c0 [c1 ...]
Examples:
rload 2 10 10k
rmod 3 7 rmodel l=10u w=1u

The nominal-temperature resistance value can be specified as a bare number, if it is the first parameter following the node list. This token can also be a resistor model name. The paramaters that can follow are:

r=expr
This can also be given as ``res=expr'' or ``resistance=expr'', where expr is an expression giving the nominal-temperature device voltage divided by device current (``large signal'' resistance) in ohms, possibly as a function of other variables. This form is applicable when the first token following the node list is not a resistance value or model name. It also applies when a model is given, it overrides the geometric resistance value.

temp=temp
The temp is the Celsius operating temperature of the resistor, for use by the temperature coefficient parameters.

tc1=tcoeff1
The first-order temperature coefficient. This will override the first-order coefficient found in a model, if given. The keyword ``tc'' is an alias for ``tc1''.

tc2=tcoeff2
The second-order temperature coefficient. This will override the second-order coefficient found in a model, if given.

l=length
The length of the resistor. This applies only when a model is given, which will compute the resistance from geometry.

w=width
The width of the resistor. This applies only when a model is given, which will compute the resistance from geometry.

noise=mult
The mult is a real number which will multiply the linear conductance used in the noise equations. Probably the major use is to give noise=0.0 to temporarily remove a resistor from a circuit noise analysis.

The second form allows specification of a polynomial resistance, which will take the form

Resistance = c0 + c1 . v + c2 . v2...
where v is the voltage difference between the positive and negative element nodes. There is no built-in limit to the number of terms.

The n1 and n2 are the two element nodes, and value is the resistance, for a constant value resistor. A resistor model modname can alternatively be specified and allows the calculation of the actual resistance value from strictly geometric information and the specifications of the process. If value is specified after modname, it overrides the geometric information (if any) and defines the nominal-temperature resistance. If modname is specified, then the resistance may be calculated from the process information in the model modname and the given length and width. In any case, the resulting value will be adjusted for the operating temperature temp if that is specified, using correction factors given. If value is not specified, then modname and length must be specified. If width is not specified, then it will be taken from the default width given in the model.

If the resistance can not be determined from the provided parameters, a fatal error results. This behavior is different from traditional Berkeley SPICE, which provides a default value of 1K.


next up previous contents index
Next: Resistor Model Up: Passive Element Lines Previous: Coupled (Mutual) Inductors   Contents   Index
Stephen R. Whiteley 2017-11-08