Question: How do I set up a temperature coefficient for a resistor? I would like
to define a resistor that has a temperature coefficient of 1500ppm/degree C.
Answer: There are two methods that can be used to define temperature coefficients
for the resistor. The first method is through the VALUE attribute of the resistor. The
VALUE attribute has the format:
[TC=<tc1>[,<tc2>]]
where the temperature coefficients are an optional entry. When these coefficients are
specified, they multiply by the following factor:
1 + <tc1>*(T-Tnom) + <tc2>*(T-Tnom)^2
As can be seen above, the <tc1> is a linear temperature coefficient and the <tc2> is a
quadratic temperature coefficient. An example for the VALUE attribute would be:
1K TC=1.5E-3
which would produce a 1500ppm/degree C coefficient for a 1K ohm resistor.
The second method to declare a temperature coefficient is through the resistor model
statement's TC1 and TC2 parameters. When in the Attribute dialog box, define the MODEL
attribute of the resistor with a model name such as RESTEMP or RMOD. Any valid name will
work. When the MODEL attribute has been defined, the model parameters at the bottom of
the Attribute dialog box become available for editing. Among these parameters are TC1
and TC2. These act in the same manner as the <tc1> and <tc2> parameters in the VALUE
attribute. Defining the TC1 parameter with the value 1.5E-3 will create the
1500ppm/degree C coefficient also. Any coefficients defined within the VALUE attribute
will take precedence over model parameters.
The capacitor and inductor each have TC1 and TC2 model parameters available in order to
create temperature coefficients when the MODEL attribute has been defined. These
parameters operate with the same behavior as the resistor's temperature parameters. The
VALUE attribute temperature coefficients are not available for these components.
The resistor model has one extra temperature coefficient parameter that the capacitor
and inductor models do not have. This parameter is TCE and defines the exponential
temperature coefficient in units of %/degree C as:
1.01 ^ (TCE*(T-Tnom))
In general, the TC1 parameter will be the value specified in databooks.
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