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@ -1770,10 +1770,10 @@ in the direction of voltage drop). |
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General form: |
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@example |
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RXXXXXXX N1 N2 VALUE <ac=val> <m=val> <scale=val> |
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RXXXXXXX n+ n- value <ac=val> <m=val> <scale=val> <dtemp = val> |
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+ <noisy = 0|1> |
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@end example |
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Examples: |
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@example |
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@ -1783,23 +1783,79 @@ in the direction of voltage drop). |
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RL 1 4 2K m=2 |
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@end example |
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Ngspice has a fairly complex model for resistors. It can simulate both |
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discrete and semiconductor resistors. Semiconductor resistors in ngspice |
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means: resistors described by geometrical parameters. So, do not expect |
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detailed modeling of semiconductor effects. |
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N1 and N2 are the two element nodes. VALUE is the resistance (in ohms) |
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and may be positive or negative but not zero. It is possible to specify |
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a different resistance value for ac calculations, using the "ac" |
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parameter. The value of ac resistance must not be zero. If you do not |
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specify the "ac" parameter, it will be defaulted to VALUE. |
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@option{n+} and @option{n-} are the two element nodes, @option{value} is the |
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resistance (in ohms) and may be positive or negative but not zero. If you |
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need to simulate very small resistors (0.001 Ohm or less) , you should use |
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CCVS (transresistance), it is less efficient but improves numerical |
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accuracy (a small resistance is a large conductance). |
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Ngspice can assign a resistor instance a different value for AC analysis, |
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specified using the @option{ac} keyword. This value must not be zero as |
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described above. The AC resistance is used in AC analysis only (not Pole-Zero |
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nor noise). If you do not specify the @option{ac} parameter, it is defaulted |
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to @option{value}. |
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The @option{m} parameter is the "multiplication factor", and can be used to |
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simulate "m" instances of the same kind in parallel. This parameter affects |
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all analyses. |
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The @option{scale} keyword let the designer choose a different scale for |
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elements. This option is not yet very useful, it will fully implemented in the |
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future to perform technology scaling. At present is here as a work in progress. |
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The operating temperature of instances can be changed using the @option{dtemp} |
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keyword. Ngspice simulates the circuit with all components at the same single |
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temperature (the circuit temperature). To adjust the temperature of a resistor |
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instance you can define its temperature difference from the rest of the |
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circuit using @option{dtemp}. |
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If you want to simulate temperature dependence of a resistor, you need to |
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specify its temperature coefficients, using a @command{.model} line, like in the |
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example below: |
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@example |
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RE1 1 2 700 std dtemp=5 |
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.MODEL std tc1=0.001 |
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@end example |
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The "m" parameter is the "multiplication factor" and scale is the "scale" |
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factor: |
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Resistance = Resistance * Scale / M |
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Setting m to "val" is like putting m equal resistance in parallel. |
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The "scale" parameter let the designer to choose a different scale |
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for elements. |
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Instance temperature is useful even if resistance does not varies with it, since |
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the thermal noise generated by a resistor depends on its absolute temperature. |
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Note: ac parameter can be considered "safe" since rework-11 |
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Scale parameter is not applied to l,w and other geometric |
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parameters. |
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Resistors in ngspice generates two different noises: thermal and flicker. While |
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thermal noise is always generated in the resistor, to add a flicker noise source |
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you have to add a @command{.model} card defining the flicker noise parameters. |
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It is possible to simulate resistors that do not generate any kind of noise |
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|
using the @option{noisy} keyword and assigning zero to it, as in the |
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|
following example: |
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|
@example |
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|
Rmd 134 57 1.5k noisy=0 |
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@end example |
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Ngspice calculates the nominal resistance as described below: |
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@tex |
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$$ |
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R_{nom} = {{{\rm VALUE} * {\rm scale}} \over m} |
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$$ |
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$$ |
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R_{acnom} = {{{\rm ac} * {\rm scale}} \over m} |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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Rnom = value * scale / m |
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Racnom = ac * scale / m |
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@end example |
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@end ifnottex |
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|
If you are interested in temperature effects or noise equations, read the |
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following section on semiconductor resistors. |
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@node Semiconductor Resistors, Semiconductor Resistor Model (R), Resistors, Elementary Devices |
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@subsection Semiconductor Resistors |
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@ -1807,8 +1863,8 @@ Note: ac parameter can be considered "safe" since rework-11 |
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|
General form: |
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|
@example |
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RXXXXXXX N1 N2 <VALUE> <MNAME> <L=LENGTH> <W=WIDTH> <TEMP=T> |
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|
m=<val> <ac=val> <scale=val> |
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|
RXXXXXXX n+ n- <value> <mname> <l=lenght> <w=width> <temp=t> |
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|
+ <dtemp=val> m=<val> <ac=val> <scale=val> <noisy = 0|1> |
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@end example |
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|
@ -1819,20 +1875,20 @@ Note: ac parameter can be considered "safe" since rework-11 |
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|
RMOD 3 7 RMODEL L=10u W=1u |
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@end example |
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|
This is the more general form of the resistor presented before (@pxref{Resistors}) |
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|
and allows the modeling of temperature effects and for the calculation of the |
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|
actual resistance value from strictly geometric information and the |
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|
specifications of the process. If @option{value} is specified, it overrides |
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|
the geometric information and defines the resistance. If @option{mname} is |
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|
specified, then the resistance may be calculated from the process information |
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|
in the model @option{mname} and the given @option{lenght} and @option{width}. |
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|
If @option{value} is not specified, then @option{mname} and @option{lenght} |
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|
must be specified. If @option{width} is not specified, then it is taken |
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|
|
from the default width given in the model. |
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|
This is the more general form of the resistor presented in section |
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|
6.1, and allows the modeling of temperature effects and for the |
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|
calculation of the actual resistance value from strictly geometric |
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|
|
information and the specifications of the process. If VALUE is |
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|
specified, it overrides the geometric information and defines the |
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|
resistance. If MNAME is specified, then the resistance may be |
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|
calculated from the process information in the model MNAME and the |
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|
given LENGTH and WIDTH. If VALUE is not specified, then MNAME and |
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|
LENGTH must be specified. If WIDTH is not specified, then it is taken |
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|
from the default width given in the model. The (optional) TEMP value |
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|
is the temperature at which this device is to operate, and overrides |
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|
the temperature specification on the .OPTION control line. |
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|
The (optional) @option{temp} value is the temperature at which this device is |
|
|
|
to operate, and overrides the temperature specification on the |
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|
@command{.option} control line and the value specified in @option{dtemp}. |
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@ -1845,63 +1901,92 @@ the resistance to be calculated from geometric information and to be |
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|
corrected for temperature. The parameters available are: |
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|
|
@multitable @columnfractions .15 .4 .2 .1 .1 |
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|
@item name @tab parameter @tab units @tab default @tab example |
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|
@item TC1 @tab first order temperature coeff. |
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|
@tab Z/°C @tab 0.0 |
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|
@item TC2 @tab second order temperature coeff. |
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|
@tab Z/°C@math{^2} @tab 0.0 |
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|
@item RSH @tab sheet resistance |
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@tab Z/[] @tab - @tab 50 |
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|
@item DEFW @tab default width |
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|
@tab meters @tab 1e-6 @tab 2e-6 |
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|
@item name @tab parameter @tab units @tab default @tab example |
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|
@item TC1 @tab first order temperature coeff. |
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|
@tab Ohm/°C @tab 0.0 |
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|
@item TC2 @tab second order temperature coeff. |
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|
@tab Ohm/°C@math{^2} @tab 0.0 |
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@item RSH @tab sheet resistance |
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@tab Ohm/[] @tab - @tab 50 |
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@item DEFW @tab default width |
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@tab meters @tab 1e-6 @tab 2e-6 |
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|
@item NARROW @tab narrowing due to side etching |
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|
@tab meters @tab 0.0 @tab 1e-7 |
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|
@tab meters @tab 0.0 @tab 1e-7 |
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|
@item SHORT @tab shortening due to side etching |
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|
@tab meters @tab 0.0 @tab 1e-7 |
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|
@item TNOM @tab parameter measurement temperature |
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|
@tab °C @tab 27 @tab 50 |
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|
@tab meters @tab 0.0 @tab 1e-7 |
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@item TNOM @tab parameter measurement temperature |
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|
@tab °C @tab 27 @tab 50 |
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@item KF @tab flicker noise coefficient |
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|
@tab - @tab 0.0 @tab 5e-15 |
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|
@item AF @tab flicker noise exponent |
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|
@tab - @tab 0.0 @tab 1.0 |
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|
@end multitable |
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|
|
The sheet resistance is used with the narrowing parameter and L and W |
|
|
|
from the resistor device to determine the nominal resistance by the |
|
|
|
formula |
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|
|
The sheet resistance is used with the narrowing parameter and @option{l} |
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|
|
and @option{w} from the resistor device to determine the nominal resistance |
|
|
|
by the formula |
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|
|
@tex |
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|
|
$$ |
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|
|
R = {\rm RSH} {L - {\rm SHORT} \over W - {\rm NARROW}} |
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|
|
R_{nom} = {\rm rsh} {l - {\rm SHORT} \over w - {\rm NARROW}} |
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|
|
$$ |
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|
|
@end tex |
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|
|
@ifnottex |
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|
|
@example |
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|
|
L - SHORT |
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|
|
R = RSH ---------- |
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|
|
W - NARROW |
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|
L - SHORT |
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|
|
Rnom = RSH ---------- |
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|
|
W - NARROW |
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|
|
@end example |
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|
|
@end ifnottex |
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|
|
DEFW is used to supply a default value for W if one is not specified for |
|
|
|
the device. If either RSH or L is not specified, then the standard |
|
|
|
default resistance value of 1k Z is used. TNOM is used to override the |
|
|
|
circuit-wide value given on the .OPTIONS control line where the |
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|
|
parameters of this model have been measured at a different temperature. |
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|
|
After the nominal resistance is calculated, it is adjusted for |
|
|
|
temperature by the formula: |
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|
|
@option{DEFW} is used to supply a default value for @option{w} if one is |
|
|
|
not specified for the device. If either @option{RSH} or @option{L} is not |
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|
|
specified, then the standard default resistance value of 1k Ohm is used. |
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|
|
@option{TNOM} is used to override the circuit-wide value given on the |
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|
|
@command{.options} control line where the parameters of this model have |
|
|
|
been measured at a different temperature. |
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|
|
After the nominal resistance is calculated, it is adjusted for temperature |
|
|
|
by the formula: |
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|
|
@tex |
|
|
|
$$ |
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|
|
R(T) = R(T_0) \Bigl( 1 + TC_1 (T - T_0) + TC_2 (T-T_0)^2 \Bigr) |
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|
|
R(T) = R({\rm TNOM}) \Bigl( 1 + TC_1 (T - {\rm TNOM}) + TC_2 (T-{\rm TNOM})^2 \Bigr) |
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|
|
$$ |
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|
|
where $R({\rm TNOM}) = R_{nom} \vert R_{acnom}$. |
|
|
|
@end tex |
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|
|
@ifnottex |
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|
|
@example |
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|
|
2 |
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|
|
R(T) = R(T ) [1 + TC (T - T ) + TC (T - T ) ] |
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|
|
0 1 0 2 0 |
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|
|
2 |
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|
|
R(T) = R(TNOM) [1 + TC (T - TNOM) + TC (T - TNOM) ] |
|
|
|
1 2 |
|
|
|
where R(TNOM) = Rnom or Racnom |
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|
|
@end example |
|
|
|
@end ifnottex |
|
|
|
|
|
|
|
In the above formula, "T" represents the instance temperature, which can be |
|
|
|
explicitly using the @option{temp} keyword or os calculated using the |
|
|
|
circuit temperature and and @option{dtemp}, if present. |
|
|
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|
|
If both @option{temp} and @option{dtemp} are specified, the latter is ignored. |
|
|
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|
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|
|
A small list of sheet resistances (in Ohm/[]) for conductors is shown below. |
|
|
|
The table represents typical values for MOS processes in the 0.5 - 1 um |
|
|
|
range. The table is taken from: @emph{N. Weste, K. Eshraghian - Principles of |
|
|
|
CMOS VLSI Design 2nd Edition, Addison Wesley}. |
|
|
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|
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|
|
@multitable @columnfractions .55 .15 .15 .15 |
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|
|
@item Material @tab Min. @tab Typical @tab Max. |
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|
|
@item Intermetal (metal1 - metal2) @tab 0.005 @tab 0.007 @tab 0.1 |
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|
|
@item Top-metal (metal 3) @tab 0.003 @tab 0.004 @tab 0.05 |
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|
|
@item Polysilicon @tab 15 @tab 20 @tab 30 |
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|
|
@item Silicide @tab 2 @tab 3 @tab 6 |
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|
|
@item Diffusion(n+,p+) @tab 10 @tab 25 @tab 100 |
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|
|
@item Silicided diffusion @tab 2 @tab 4 @tab 10 |
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|
|
@item n-well @tab 1000 @tab 2000 @tab 5000 |
|
|
|
@end multitable |
|
|
|
|
|
|
|
|
|
|
|
@node Capacitors, Semiconductor Capacitors, Semiconductor Resistor Model (R), Elementary Devices |
|
|
|
@subsection Capacitors |
|
|
|
@ -6112,7 +6197,38 @@ values above may be node names in the running circuit, or real values. |
|
|
|
If more than one condition is given, e.g. stop after 4 when @math{v(1) > 4} |
|
|
|
when @math{v(2) < 2}, the conjunction of the conditions is implied. |
|
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|
|
@subsection Sysinfo: Print system information |
|
|
|
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|
|
|
General Form: |
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|
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|
|
|
|
@example |
|
|
|
sysinfo |
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|
|
@end example |
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|
|
The command prints system information useful for sending bug report |
|
|
|
to developers. Information consists of: |
|
|
|
|
|
|
|
@itemize @bullet |
|
|
|
@item Name of the operating system, |
|
|
|
@item Name of the node, |
|
|
|
@item Current release of the operating system, |
|
|
|
@item Current version of this release, |
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|
|
@item Name of hardware type. |
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|
|
@end itemize |
|
|
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|
|
|
|
The example below shows the use of this command. |
|
|
|
|
|
|
|
@example |
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|
|
ngspice 1 -> sysinfo |
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|
|
Linux janus.wayout.net 2.4.20 #1 SMP Tue Jun 10 18:58:26 CEST 2003 i686 |
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|
|
ngspice 2 -> |
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|
|
@end example |
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|
|
@strong{Note:} This command may not be available on your environment, if |
|
|
|
it is not available, please send analogous information when submitting |
|
|
|
bug reports. |
|
|
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|
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|
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|
|
@node Tf, Trace, Stop, Commands |
|
|
|
@subsection Tf*: Run a Transfer Function analysis |
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|
|
|
pnenzi
23 years ago