## 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

NoteFor RFDE Users Information about this model must be provided in a model file; refer to Netlist Format. |

- This model supplies values for a Diode device.
- 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. **Area and Periph**

(standard):*When Level is set to 1*

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 - Etch1otherwise 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 - Etch1otherwise 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).

**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).**Currents and Conductances**

Is and Isr in the following equations have been multiplied by the effective area factor aeff.

If vd > vmaxidexp = [Imax + (vd - vmax) × gmax]

gdexp = gmaxwhere

vt is thermal voltageIf 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 = gbmaxwhere

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

Otherwise

ib = 0

gb = 0For 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 = glbmaxwhere

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

Otherwise

ilb = 0

glb = 0For ilbo

If Bv < MAXEXP × Nbvl × vt

Otherwise

ilbo = 0

Recombination current is considered if Isr is specified and not equal to zero.

If vd > vrmaxir = ExplI + (vd - vrmax) × grmax

| gr = grmaxwhere

If vrmax ≥ vd ≥ - 10 × Nr × vtIf vd < - 10 × Nr × vt

iexp = idexp + ib + ilb

gexp = gdexp + gb + glbThere 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 + Gminwhere 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 = gmaxswwhere

vdsw is sidewall diode voltage

vt is thermal voltageIf 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 = gbmaxswwhere

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

Otherwise

ibsw = 0

gbsw = 0For 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 + gbThere 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**Diode Capacitances**

For main diode capacitance

Diffusion capacitanceCdiff = Tt × gdexp

Junction capacitance

If vd ≤ Fc × Vj

If Vd > Fc × Vj

Total main capacitanceCdj = Cdiff + Cj + Cd × Area

For sidewall capacitance

If vdsw ≤ Fcsw × Vjsw

If vdsw > Fcsw × Vjsw

**Temperature Scaling**

Parameters Is, Jsw, Isr, Cjo, Cjsw, Vj, Vjsw, Bv, Tt, and Rs are temperature dependent.

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.)**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 energy bandgap

*E*varies as:_{G}

if*Tlev*= 0, 1

if*Tlev*= 2

The intrinsic carrier concentration*n*for silicon varies as:_{i}

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 = 0if Tlevc = 1

if Tlevc = 2

if Tlevc = 3if Tlev = 2

if Tlev = 0 or Tlev = 1

The junction grading coefficient M scales as:

The sidewall grading coefficient Msw does not scale.**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.- 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.
- 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

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

##### Equivalent Circuit

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