Two-Terminal Capacitor (capacitor)

You can assign the capacitance or let Spectre compute it from the physical length and width of the capacitor. In either case, the capacitance can be a function of temperature or applied voltage.

This device is supported within altergroups.

If the C(inst) is not given,

    C(inst) = C(model)

if C(model) is given,

and if Area(inst) or Perim(inst) is given

Area_eff = Area - (Perim)*etch + 4*etch^2

Perim_eff = Perim - 8*etch

else

Area_eff  = (L - 2*etch)*(W - 2*etch)

Perim_eff = 2 *(W + L - 4*etch)

C(inst) = Cj*Ar    ea_eff +  Cjsw*Perim_eff

if C(model) is not given.

If the polynomial coefficients vector (coeffs=[c1 c2 ...]) is specified, the capacitor is nonlinear and the capacitance is

    C(V) = dQ(V) / dV

         = C(inst)*(1 + c1*V + c2*V^2 + ...)

Q(V) = C(inst)*V*(1 + 1/2*c1*V + 1/3*c2*V^2 + ...)

where ck is the kth entry in the coefficient vector.

The value of the capacitor as a function of the temperature is given by:

C(T) = C(tnom)*[1 + tc1*(T - tnom) + tc2*(T - tnom)^2]

where

T = trise(inst) + temp

if trise(inst) is given, and

T = trise(model) + temp

if trise(inst) is not given.

Sample Instance Statement

without model:

c2 (1 0) capacitor c=2.5u tc1=1e-8

with model:

c2 (1 0) proc_cap c=2.5u tc1=1e-8

Sample Model Statement

model proc_cap capacitor c=2u tc1=1.2e-8 tnom=25

This device supports behavior expression

Sample Behavior Statement

c1 (1 0) capacitor c=c0*(1 + tanh(v(1,2)*c2))

c1 (1 0) capacitor c=1e-12/(1+($freq)/1e9)

Instance Syntax

Name  1  2 ModelName parameter=value ...

Name  1  2 capacitor parameter=value ...

Instance Parameters


`c`	`(F)`	Capacitance.
`c0`	`(F)`	0th order value of polynomial capacitor.
`w`	`(m)`	Capacitor width.
`l`	`(m)`	Capacitor length.
`m`	`1`	Multiplicity factor.
`scale`	`1`	Scale factor.
`trise`	`(C)`	Temperature rise from ambient.
`tc1`	`(1/C)`	Linear temperature coefficient.
`tc2`	`(C`^-2`)`	Quadratic temperature coefficient.
`ic`	`(V)`	Initial condition(alias=lv2).
`area`	`1.0 m`²	Capacitor area.
`perim`	`0.0 m`	Capacitor perimeter.
`coeffs`	`[...]`	Vector of polynomial capacitance coefficients.
`symmetric`	`none`	Use symmetric capacitor model.Possible values are none and absolute.
`bv_max`	`infinity V`	Maximum allowed voltage cross two terminals.
`scalec`		Capacitance scaling factor.
`bv_min`	`-infinity V`	Minimum allowed voltage cross two terminals.

The instance parameter scale, if specified, overrides the value given by the option parameter scale. The w and l parameters are scaled by the resulting scale, and the option parameter scalem. The values of w and l printed by Spectre are those given in the input file, and these values might not have the correct units if the scaling factors are not unity. The correct capacitor dimensions are stored in the output parameters. You can obtain these dimensions with the info statement.

Model Syntax

model modelName capacitor parameter=value ...

Model Parameters


`c`	`0 F`	Default capacitance.
`trise`	`0 C`	Default `trise` value for instance.
`tnom`	`(C)`	Parameter measurement temperature. The default value is set using the options statement.
`w`	`0 m`	Default capacitor width.
`l`	`0 m`	Default capacitor length.
`etch`	`0 m`	Narrowing due to side etching.
`cj`	`0 F/m`²	Bottom capacitance density.
`cjsw`	`0 F/m`	Sidewall capacitance.
`scalec`	`1`	Capacitance scaling factor.
`rforce`	`1` Ω	Resistance used when forcing initial conditions.
`di`	`0`	Relative dielectric constant.
`thick`	`0 m`	Dielectric thickness.

Polynomial capacitor parameters


`coeffs`	`[...]`	Vector of polynomial capacitance coefficients.
`symmetric`	`none`	Use symmetric resistor model.Possible values are none and absolute.
`min`	`(F)`	Minimum capacitance.
`max`	`(F)`	Maximum capacitance.

Temperature effects parameters


`tc1`	`0 1/C`	Linear temperature coefficient.
`tc2`	`0 C`^-2	Quadratic temperature coefficient.

Shrink Parameters


`shrink`	`0.0`	Linear shrink parameter.
`shrink2`	`0.0`	Area shrink parameter.

Safe Operating Areas Parameters


`bv_max`	`infinity V`	Maximum allowed voltage across two terminals.
`bv_min`	`-infinity V`	Minimum allowed voltage across two terminals.

Output Parameters


`tempeff`	`(C)`	Effective temperature for a single device.
`meff`		Effective multiplicity factor (m-factor).
`leff`	`(m)`	Effective capacitor length.
`weff`	`(m)`	Effective capacitor width.
`ceff`	`(F)`	Effective capacitance(alias=lv1).

Spectre Circuit Simulator Components and Device Models Reference
Product Version 23.1, June 2023