Diode_Model (PN-Junction Diode Model)

Symbol

Available in ADS and RFDE

Supported via model include file in RFDE

Parameters


Model parameters must be specified in SI units.

Name Description Units Default
Level Model level selector (1=standard, 3=Hspice geometry 11=Spectre) None 1
Is (Js) †, †† Saturation Current, A (with N, determines diode DC characteristics) A 1.0e-14
Rs ††† Ohmic Resistance Ohm fixed at 0
Gleak Bottom junction leakage conductance S 0
N Emission Coefficient (with Is, determines diode DC characteristics) None 1.0
Tt Transit Time sec 0.0
Cd Linear capacitance F 0.0
Cjo †, †† Zero-bias Junction capacitance F 0.0
Vj (Pb) †† Junction Potential V 1.0
M Grading Coefficient None fixed at 0.5
Fc Forward-bias Depletion Capacitance Coefficient None 0.5
Imax Explosion current beyond which diode junction current is linearized A 1.0
Imelt Explosion current (similar to Imax; refer to Note 4); defaults to Imax A defaults to Imax
Isr †, †† Recombination current A 0.0
Nr Emission coefficient for Isr None 2.0
Ikf (Ik) High-injection knee current A infinity
Ikr Reverse high injection knee current A 0
IkModel Model to use for Ikf/Ikr: 1=ADS/Libra/Pspice, 2=Hspice/Spectre None 1
Bv Reverse breakdown voltage V infinity
Ibv Current at reverse breakdown voltage A 0.001
Nbv (Nz) Reverse breakdown ideality factor None 1.0
Ibvl Low-level reverse breakdown knee current A 0.0
Nbvl Low-level reverse breakdown ideality factor None 1.0
Kf Flicker noise coefficient None 0.0
Af Flicker noise exponent None 1.0
Ffe Flicker noise frequency exponent None 1.0
Jsw (Isw) †† ‡‡ Sidewall saturation current None 0.0
Rsw ‡‡‡ Sidewall series resistance Ohm 0.0
Gleaksw ‡‡ Sidewall junction leakage conductance S 0.0
Ns Sidewall emission coefficient None if (Level=11) Ns=1, else Ns=N
Ikp ‡‡ high-injection knee current for sidewall; defaults to Ikf A Ikf
Cjsw †† ‡‡ Sidewall zero-bias capacitance None 0.0
Msw (Mjsw) Sidewall grating coefficient None 0.33
Vjsw (Pbsw) †† Sidewall junction potential; defaults to Vj None 1: when level=11; defaults to Vj
Fcsw Sidewall forward-bias depletion capacitance coefficient None 0.5; Fc: when level=11
Area Default area for diode None 1
Periph (Perim) Default periphery for diode None 0
Width Default width for diode meter 0
Length Default length for diode meter 0
Etch Sidewall narrowing due to etching per side meter 0
Etchl Sidewall length reduction due to etching per side; defaults to Etch meter defaults to Etch
Dwl Geometry width and length addition meter 0
Shrink Geometry shrink factor None 1.0
AllowScaling Allow scale option and instance scale parameter to affect geometry parameters: yes or no None no
Tnom Nominal ambient temperature o C 25
Trise Temperature rise over ambient °C 0
Tlev Temperature equation selector (0/1/2) None 0
Tlevc Temperature equation selector for capacitance (0/1/2/3) None 0
Xti Saturation-current temperature exponent (with Eg, helps define the dependence of Is on temperature) None 3.0
Eg Energy gap (with Xti, helps define the dependence of Is on temperature) eV 1.11
EgAlpha (Gap1) Energy gap temperature coefficient alpha eV/ o C 7.02e-4
EgBeta (Gap2) Energy gap temperature coefficient beta K 1108
Tcjo (Cta) Cjo linear temperature coefficient 1/ o C 0
Tcjsw (Ctp) Cjsw linear temperature coefficient 1 o/ C 0
Ttt1 Tt linear temperature coefficient 1/ o C 0
Ttt2 Tt quadratic temperature coefficient 1/( o C) 2 0
Tm1 Mj linear temperature coefficient 1/ o C 0
Tm2 Mj quadratic temperature coefficient 1/( o C) 2 0
Tvj (Pta) Vj linear temperature coefficient 1/ o C 0
Tvjsw (Ptp) Vjsw linear temperature coefficient 1/ o C 0
Trs Rs linear temperature coefficient 1/ o C 0
Trs2 Rs quadratic temperature coefficient 1/( o C) 2 0
Tgs Gleak, Gleaksw linear temperature coefficient 1/ o C 0
Tgs2 Gleak, Gleaksw quadratic temperature coefficient 1/( o C) 2 0
Tbv (Tbv1) Bv linear temperature coefficient 1/ o C 0
Tbv2 Bv quadratic temperature coefficient 1/( o C) 2 0
wBv (Bvj) Diode reverse breakdown voltage (warning) V infinity
wPmax Maximum power dissipation (warning) W infinity
AllParams Data Access Component (DAC) Based Parameters None None
Parameter value is scaled with Area specified with the Diode device. †† Value varies with temperature based on model Tnom and device Temp. ††† Parameter value is scaled with 1/Area. Value 0.0 is interpreted as infinity. ‡‡ Parameter value is scaled with the Periph specified with the Diode device. ‡‡‡ Parameter value is scaled with 1/Periph.


Netlist Format

Model statements for the ADS circuit simulator may be stored in an external file. This is typically done with foundry model kits. For more information on how to set up and use foundry model kits, refer to the Design Kit Development manual.

model modelname Diode [parm=value]*

The model statement starts with the required keyword diode . It is followed by the modelname that will be used by diode components to refer to the model. The third parameter indicates the type of model; for this model it is Diode . The rest of the model contains pairs of model parameters and values, separated by an equal sign. The name of the model parameter must appear exactly as shown in the parameters table-these names are case sensitive. Some model parameters have aliases, which are listed in parentheses after the main parameter name; these are parameter names that can be used instead of the primary parameter name. Model parameters may appear in any order in the model statement. Model parameters that are not specified take the default value indicated in the parameters table. For more information about the ADS circuit simulator netlist format, including scale factors, subcircuits, variables and equations, refer to "ADS Simulator Input Syntax" in the Using Circuit Simulators manual.

Example:

model SimpleDiode Diode \
Is=1e-9 Rs=4 Cjo=1.5e-12

Notes/Equations
Note
For RFDE Users Information about this model must be provided in a model file; refer to Netlist Format.
  1. This model supplies values for a Diode device.
  2. Use AllParams with a DataAccessComponent to specify file-based parameters (refer to "DataAccessComponent" in Chapter 5 of the Introduction to Circuit Components manual). Note that model parameters that are explicitly specified take precedence over those specified via AllParams.
  3. Area and Periph
    When Level is set to 1 (standard):
    Device Area will be used if specified and > 0; otherwise the model Area will be used.

    Device Periph will be used if specified; otherwise the model Periph will be used.
    When Level is set to 3 (Hspice geometry):

    Device Width and Length will be used if specified; otherwise the model Width and Length will be used.

    If Width > 0 and Length > 0

    Area = w × l
    Periph = 2 × (w + l)
    where w = Width × Shrink + Dwl
    l = Length × Shrink + Dwl
    otherwise the Area and Periph specified in the device or model
    (follow the same logic described when Level=1)
    will be used to calculate the new area and periph.

    Area = area (from device/model) × Shrink 2
    Periph = periph (from device/model) × Shrink

    When Level is set to 11 (Spectre):

    Device Area will be used if it is specified and > 0;

    Otherwise

    if Length and Width in device or model (in this order) are specified and > 0,

    Area = Weff  ×  Leff
    where
    Weff = Width - Etch
    Leff = Length - Etch1

    otherwise use model Area if it is specified and > 0

    otherwise, Area = 1 (default)

    Device Periph will be used if it is specified and > 0

    Otherwise,

    if Length and Width in device or model (in this order) are specified and > 0,

    Periph = 2  ×  (Weff + Leff)
    where
    Weff = device Width - Etch
    Leff = device Length - Etch1

    otherwise use model Periph if it is specified and > 0
    otherwise, Periph = 0 (default)

    If model parameter Allowscaling is set to yes, the diode geometry parameters Periph, Width, and Length are multiplied by Scale, while Area is multiplied by Scale  ×  Scale (for Level = 11 only).

  4. Imax and Imelt Parameters
    Imax and Imelt specify the P-N junction explosion current ExplI which is used in the following equations. Imax and Imelt can be specified in the device model or in the Options component; the device model value takes precedence over the Options value. If the Imelt value is less than the Imax value, the Imelt value is increased to the Imax value.
    If Imelt is specified (in the model or in Options) ExplI = Imelt; otherwise, if Imax is specified (in the model or in Options) ExplI = Imax; otherwise, ExplI = model Imelt default value (which is the same as the model Imax default value).
  5. Currents and Conductances
    Is and Isr in the following equations have been multiplied by the effective area factor aeff.
    If vd > vmax

    idexp = [Imax + (vd - vmax) × gmax]
    gdexp = gmax

    where


    vt is thermal voltage

    If vmax ≥ vd ≥ - 10 × N × vt

    If vd < -10 × N × vt

    Breakdown current contribution is considered if Bv is specified and Ibv is not equal to zero.

    If -(vd + Bv) > vbmax

    ib= -{ExplI + [-(vd + Bv) - vbmax] × gbmax - ibo}
    gb = gbmax

    where

    If vbmax ≥ -(vd + Bv) > -MAXEXP × Nbv × vt

    Otherwise

    ib = 0
    gb = 0

    For ibo

    If Bv < MAXEXP × Nbv × vt

    Otherwise

    ibo = 0

    MAXEXP is the maximum exponent supported by the machine; value range is 88 to 709.
    Low level reverse breakdown current is considered if Ibvl is specified and not equal to zero.

    If -(vd + Bv) > vlbmax

    ilb = -{ExplI + [-(vd + Bv) - vlbmax] × glbmax - ilbo}
    glb = glbmax

    where


    If vlbmax ≥ -(vd + Bv) > - MAXEXP × Νbvl × vt

    Otherwise

    ilb = 0
    glb = 0

    For ilbo
    If Bv < MAXEXP × Nbvl × vt

    Otherwise

    ilbo = 0

    Recombination current is considered if Isr is specified and not equal to zero.
    If vd > vrmax

    ir = ExplI + (vd - vrmax) × grmax
    | gr = grmax

    where


    If vrmax ≥ vd ≥ - 10 × Nr × vt

    If vd < - 10 × Nr × vt

    iexp = idexp + ib + ilb
    gexp = gdexp + gb + glb

    There are two ways to model high-injection effect.

    When IkModel is set to ADS/Libra/Pspice and when Ikf ≠ 0 and iexp > 0.

    When IkModel is set to Hspice:
    If Ikf is not equal to zero and iexp > 0

    Otherwise if Ikr is not equal to zero and iexp < 0

    The total diode DC current and conductance

    id = idh + ir
    Id = id + Gleak × vd + Gmin × vd
    gd = gdh + gr
    Gd = gd + Gleak + Gmin

    where Gmin is minimum junction conductance.

    Sidewall diode:

    Sidewall diode equations have been multiplied by Periph, Isw, Ibv, Ikp, Gleaksw.

    If vdsw > vmaxsw

    idexpsw = [ExplI + (vdsw - vmaxsw) × gmaxsw]
    gdexpsw = gmaxsw

    where

    vdsw is sidewall diode voltage


    vt is thermal voltage

    If vmaxsw ≥ vdsw ≥ - 10 × Ns × vt

    If vdsw < -10 × Ns × vt

    Breakdown current contribution is considered if Bv is specified and Ibv ≠ 0 and Level  ≠ 11.

    If -(vdsw + Bv) > vbmaxsw

    ibsw = -{ExplI + [-(vdsw + Bv) - vbmaxsw] × gbmaxsw - ibosw}
    gbsw = gbmaxsw

    where

    If vbmaxsw ≥ -(vd + Bv) > -MAXEXP × Nbv × vt

    Otherwise

    ibsw = 0
    gbsw = 0

    For ibosw

    If (vd + Bv) < MAXEXP × Nbv × vt

    Otherwise

    ibosw = 0

    MAXEXP is the maximum exponent supported by the machine; value range is 88 to 709.

    iexpsw = idexpsw + ibsw
    gexp = gdexp + gb

    There are two ways to model sidewall diode high-injection effect.

    When IkModel is set to ADS/Libra/Pspice and when Ikp  ≠  0 and iexp > 0.


    When IkModel is set to Hspice:

    If Ikp  ≠  0 and iexp > 0

    The total diode DC current and conductance

    Idsw = idsw + Gleaksw × vdsw + Gmin × vdsw
    Gdsw = gdsw + Gleaksw + Gmin

  6. Diode Capacitances
    For main diode capacitance
    Diffusion capacitance

    Cdiff = Tt × gdexp

    Junction capacitance
    If vd ≤ Fc × Vj

    If Vd > Fc × Vj

    Total main capacitance

    Cdj = Cdiff + Cj + Cd × Area

    For sidewall capacitance
    If vdsw ≤ Fcsw × Vjsw

    If vdsw > Fcsw × Vjsw

  7. Temperature Scaling
    Parameters Is, Jsw, Isr, Cjo, Cjsw, Vj, Vjsw, Bv, Tt, and Rs are temperature dependent.
    Note
    Expressions for the temperature dependence of the energy bandgap and the intrinsic carrier concentration are for silicon only. Depletion capacitance for non-silicon diodes may not scale properly with temperature, even if values of Eg and Xti are altered from the default values given in the parameters list.
    The model specifies Tnom, the nominal temperature at which the model parameters were calculated or extracted. To simulate the device at temperatures other than Tnom, several model parameters must be scaled with temperature. The temperature at which the device is simulated is specified by the device item Temp parameter. (Temperatures in the following equations are in Kelvin.)

    The energy bandgap E G varies as:

    if Tlev = 0, 1

    if Tlev = 2
    The intrinsic carrier concentration n i for silicon varies as:

    The saturation currents Is, Isr, and Jsw scale as:

    if Tlev = 0 or Tlev = 1

    else if Tlev = 2


    The breakdown voltage Bv scales as:

    if Tlev = 0

    if Tlev = 1 or Tlev = 2


    The breakdown current Ibv does not scale with temperature.

    The transit time Tt scales as:


    The series resistance Rs scales as:

    The depletion capacitances Cjo and Cjsw and the junction potentials Vj and Vjsw vary as:
    if Tlevc = 0

    if Tlevc = 1

    if Tlevc = 2


    if Tlevc = 3

    if Tlev = 2

    if Tlev = 0 or Tlev = 1


    The junction grading coefficient M scales as:


    The sidewall grading coefficient Msw does not scale.

  8. Noise Model
    Thermal noise generated by resistor Rs is characterized by the following spectral density:

    Shot noise and flicker noise (Kf, Af, Ffe) generated by the DC current flow through the diode is characterized by the following spectral density:

    In the preceding expressions, k is Boltzmann's constant, T is the operating temperature in Kelvin, q is the electron charge, Kf , Af , and Ffe are model parameters, f is the simulation frequency, and Δ f is the noise bandwidth.

  9. The sidewall model parameters model a second ideal diode that scales with the instance parameter Periph, in parallel with the main diode that scales with the instance parameter Area. The series resistance Rs scales only with Area, not with Periph.
  10. To model a Zener diode, the model parameters Bv and Ibv can be used. Bv should be set to the Zener reverse breakdown voltage as a positive number. Ibv is set to the breakdown current that flows at that voltage as a positive number; typically this is in the range of 1 to 10 mA. The series resistance Rs should also be set; a typical value is 1 Ohm.

References
  1. Antognetti and G. Massobrio. Semiconductor device modeling with SPICE , New York: McGraw-Hill, Second Edition 1993.

Equivalent Circuit

 

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