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@ -1,4 +1,4 @@ |
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bg\input texinfo @c -*-texinfo-*- |
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\input texinfo @c -*-texinfo-*- |
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@c %**start of header |
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@setfilename ngspice.info |
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@settitle NGSPICE User Manual |
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@ -1770,8 +1770,8 @@ in the direction of voltage drop). |
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General form: |
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@example |
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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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RXXXXXXX n+ n- value <ac=val> <m=val> <scale=val> <temp=val> |
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+ <dtemp=val> <noisy=0|1> |
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@end example |
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Examples: |
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@ -1863,7 +1863,7 @@ following section on semiconductor resistors. |
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General form: |
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@example |
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RXXXXXXX n+ n- <value> <mname> <l=lenght> <w=width> <temp=t> |
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RXXXXXXX n+ n- <value> <mname> <l=length> <w=width> <temp=val> |
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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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@ -1881,8 +1881,8 @@ 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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in the model @option{mname} and the given @option{length} and @option{width}. |
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If @option{value} is not specified, then @option{mname} and @option{length} |
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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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@ -2033,10 +2033,10 @@ CMOS VLSI Design 2nd Edition, Addison Wesley}. |
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General form: |
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@example |
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CXXXXXXX N+ N- VALUE <IC=INCOND> |
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CXXXXXXX n+ n- <value> <mname> <m=val> <scale=val> <temp=val> |
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+ <dtemp=val> <ic=init_condition> |
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@end example |
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Examples: |
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@example |
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@ -2044,15 +2044,69 @@ CMOS VLSI Design 2nd Edition, Addison Wesley}. |
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COSC 17 23 10U IC=3V |
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@end example |
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Ngspice provides a detailed model for capacitors. Capacitors in the netlist can |
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be specified giving their capacitance or their geometrical and physical |
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characteristics. Following the original spice3 "convention", capacitors |
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specified by their geometrical or physical characteristics are called |
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"semiconductor capacitors" and are described in the next section. |
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N+ and N- are the positive and negative element nodes, respectively. |
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VALUE is the capacitance in Farads. |
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In this first form @option{n+} and @option{n-} are the positive and negative |
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element nodes, respectively and @option{value} is the capacitance in Farads. |
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Capacitance can be specified in the instance line as in the examples above or |
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in a @command{.model} line, as in the example below: |
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@example |
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C1 15 5 cstd |
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C2 2 7 cstd |
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.model cstd cap=3n |
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@end example |
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Both capacitors have a capacitance of 3nF. |
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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 capacitor |
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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 capacitor, 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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CEB 1 2 1u cap1 dtemp=5 |
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.MODEL cap1 tc1=0.001 |
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@end example |
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The (optional) initial condition is the initial (timezero) value of |
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capacitor voltage (in Volts). Note that the initial conditions (if any) |
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apply 'only' if the UIC option is specified on the .TRAN control line. |
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apply 'only' if the @option{uic} option is specified on the @command{.tran} |
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control line. |
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Ngspice calculates the nominal capacitance as described below: |
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@tex |
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$$ |
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C_{nom} = {{{\rm value} * {\rm scale}} * m} |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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Cnom = value * scale * m |
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@end example |
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@end ifnottex |
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@node Semiconductor Capacitors, Semiconductor Capacitor Model (C), Capacitors, Elementary Devices |
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@ -2061,7 +2115,8 @@ apply 'only' if the UIC option is specified on the .TRAN control line. |
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General form: |
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@example |
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CXXXXXXX N1 N2 <VALUE> <MNAME> <L=LENGTH> <W=WIDTH> <IC=VAL> |
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CXXXXXXX n+ n- <value> <mname> <l=length> <w=width> <m=val> |
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+ <scale=val> <temp=val> <dtemp=val> <ic=init_condition> |
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@end example |
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@ -2073,17 +2128,15 @@ apply 'only' if the UIC option is specified on the .TRAN control line. |
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@end example |
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This is the more general form of the Capacitor presented in section 6.2, |
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and allows for the calculation of the actual capacitance value from |
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strictly geometric information and the specifications of the process. |
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If VALUE is specified, it defines the capacitance. If MNAME is |
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specified, then the capacitance is calculated from the process |
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information in the model MNAME and the given LENGTH and WIDTH. If VALUE |
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is not specified, then MNAME and LENGTH must be specified. If WIDTH is |
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not specified, then it is taken from the default width given in the |
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model. Either VALUE or MNAME, LENGTH, and WIDTH may be specified, but |
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not both sets. |
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This is the more general form of the Capacitor presented in section |
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(@pxref{Capacitors}), and allows for the calculation of the actual capacitance |
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value from strictly geometric information and the specifications of the process. |
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If @option{value} is specified, it defines the capacitance and both process and |
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geometrical information are discarded. If @option{value} is not specified, the |
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capacitance is calculated from information contained model @option{mname} and |
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the given length and width (@option{l}, @option{w} keywords, respectively). |
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It is possible to specify @option{mname} only, without geometrical dimensions |
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and set the capacitance in the @command{.model} line (@pxref{Capacitors}). |
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@ -2096,34 +2149,168 @@ The capacitor model contains process information that may be used to |
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compute the capacitance from strictly geometric information. |
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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 CJ @tab junction bottom capacitance |
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@tab F/meters@math{^2} @tab - @tab 5e-5 |
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@item CJSW @tab junction sidewall capacitance |
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@tab F/meters @tab - @tab 2e-11 |
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@item DEFW @tab default device 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 CAP @tab model capacitance |
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@tab F @tab 0.0 @tab 1e-6 |
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@item CJ @tab junction bottom capacitance |
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@tab F/meters@math{^2} @tab - @tab 5e-5 |
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@item CJSW @tab junction sidewall capacitance |
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@tab F/meters @tab - @tab 2e-11 |
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@item DEFW @tab default device width |
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@tab meters @tab 1e-6 @tab 2e-6 |
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@item DEFL @tab default device length |
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@tab meters @tab 0.0 @tab 1e-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 shorting due to side etching |
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@tab meters @tab 0.0 @tab 1e-7 |
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@item TC1 @tab first order temperature coeff. |
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@tab F/°C @tab 0.0 @tab 0.001 |
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@item TC2 @tab second order temperature coeff. |
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@tab F/°C@math{^2} @tab 0.0 @tab 0.0001 |
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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 DI @tab relative dielectric constant |
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@tab F/m @tab 0.0 @tab 1 |
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@item THICK @tab insulator thickness |
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@tab meters @tab 0.0 @tab 1e-9 |
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@end multitable |
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The capacitor has a capacitance computed as |
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The capacitor has a capacitance computed as: |
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If @option{value} is specified on the instance line then |
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@tex |
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$$ |
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C_{nom} = {{{\rm value} * {\rm scale}} * m} |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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Cnom = value * scale * m |
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@end example |
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@end ifnottex |
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If model capacitance is specified then |
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@tex |
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$$ |
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C_{nom} = {{{\rm CAP} * {\rm scale}} * m} |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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Cnom = CAP * scale * m |
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@end example |
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@end ifnottex |
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If neither @option{value} nor @option{CAP} are specified, then geometrical and |
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physical parameters are take into account: |
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@tex |
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$$ |
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{\rm C_{0}} = {\rm CJ} (l - {\rm SHORT}) |
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(w - {\rm NARROW}) + |
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2 {\rm CJSW} (l - {\rm SHORT} + w - {\rm NARROW}) |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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C0 = CJ (l - NARROW) (w - NARROW) + |
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2 CJSW (l - SHORT + w - NARROW) |
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@end example |
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@end ifnottex |
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@option{CJ} can be explicitly given on the @command{.model} line or calculated |
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by physical parameters. When @option{CJ} is not given, is calculated as: |
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If @option{THICK} is not zero: |
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@tex |
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if {\rm DI } is specified: |
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$$ |
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{\rm CJ } = {{{\rm DI} * \epsilon_{0}} \over {\rm THICK} } |
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$$ |
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otherwise: |
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$$ |
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{\rm CJ } = {{ \epsilon_{SiO_{2}}} \over {\rm THICK} } |
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$$ |
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with: |
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$$ |
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\epsilon_{0} = 8.854214871e-12 {F \over m} |
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$$ |
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$$ |
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\epsilon_{SiO_{2}} = 3.4531479969e-11 {F \over m} |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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DI * eps |
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0 |
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CJ = --------- if DI is specified |
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THICK |
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eps |
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SiO |
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2 |
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CJ = --------- if DI is not specified |
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THICK |
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with: |
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eps = 8.854214871e-12 F/m |
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0 |
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eps = 3.4531479969e-11 F/m |
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SiO |
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2 |
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@end example |
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@end ifnottex |
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@tex |
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$$ |
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C_{nom} = {C_{0} * {\rm scale} * m} |
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$$ |
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@end tex |
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@ifnottex |
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@example |
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Cnom = C0 * scale * m |
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@end example |
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@end ifnottex |
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After the nominal capacitance is calculated, it is adjusted for temperature |
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by the formula: |
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@tex |
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$$ |
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{\rm CAP} = {\rm CJ} ({\rm LENGTH} - {\rm NARROW}) |
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({\rm WIDTH} - {\rm NARROW}) + |
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2 {\rm CJSW} ({\rm LENGTH} + {\rm WIDTH} - 2 {\rm NARROW}) |
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C(T) = C({\rm TNOM}) \Bigl( 1 + TC_1 (T - {\rm TNOM}) + TC_2 (T-{\rm TNOM})^2 \Bigr) |
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$$ |
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where $C({\rm TNOM}) = C_{nom}$. |
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@end tex |
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@ifnottex |
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@example |
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CAP = CJ (LENGTH - NARROW) (WIDTH - NARROW) + |
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2 CJSW (LENGTH + WIDTH - 2 NARROW) |
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2 |
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C(T) = C(TNOM) [1 + TC (T - TNOM) + TC (T - TNOM) ] |
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1 2 |
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where C(TNOM) = Cnom |
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@end example |
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@end ifnottex |
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In the above formula, "T" represents the instance temperature, which can be |
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explicitly using the @option{temp} keyword or os calculated using the |
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circuit temperature 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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@node Inductors, Coupled (Mutual) Inductors, Semiconductor Capacitor Model (C), Elementary Devices |
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@subsection Inductors |
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pnenzi
23 years ago