D. Diode

Symbol Names: DIODE, ZENER, SCHOTTKY, VARACTOR, LED, TVS.

Syntax: Dnnn anode cathode <model> [area] [off] [m=<val>] [n=<val>] [temp=<value>]

Examples:

D1 SW OUT MyIdealDiode

.model MyIdealDiode D(Ron=.1 Roff=1Meg Vfwd=.4)

D2 SW OUT dio2

.model dio2 D(Is=1e-10)

Instance parameter M sets the number of parallel devices while instance parameter N sets the number of series devices.

A diode requires a .model card to specify its characteristics. There are two types of diodes available. One is a conduction region-wise linear model that yields a computationally light weight representation of an idealized diode. It has three linear regions of conduction: on, off and reverse breakdown. Forward conduction and reverse breakdown can non-linear by specifying a current limit with Ilimit(revIlimit). tanh() is used to fit the slope of the forward conduction to the limit current. The parameters epsilon and revepsilon can be specified to smoothly switch between the off and conducting states. A quadratic function is fit between the off and on state such that the diode's I-V curve is continuous in value and slope and the transition occurs over a voltage specified by the value of epsilon for the off to forward conduction and revepsilon for the transition between off and reverse breakdown.

Below are the model parameters for this type of diode:

NameDescriptionUnitsDefault
RonResistance in forward conductionΩ1.
RoffResistance when offΩ1./Gmin
VfwdForward threshold voltage to enter conductionV0.
VrevReverse breakdown voltageVInfin.
RrevBreakdown impedanceΩRon
IlimitForward current limitAInfin.
RevilimitReverse current limitAInfin.
EpsilonWidth of quadratic regionV0.
RevepsilonWidth of reverse quad. regionV0.

This idealized model is used if any of Ron, Roff, Vfwd, Vrev or Rrev is specified in the model.

The other model available is the standard Berkeley SPICE semiconductor diode but extended to handle more detailed breakdown behavior and recombination current. The area factor determines the number of equivalent parallel devices of a specified model. Below are the diode model parameters for this diode.

Name Description Units Default Example
Is saturation current A 1e-14 1e-7
Rs Ohmic resistance Ω 0. 10.
N Emission coefficient - 1. 1.
Tt Transit-time sec 0. 2n
Cjo Zero-bias junction cap. F 0. 2p
Vj Junction potential V 1. .6
M Grading coefficient - 0.5 0.5
Eg Activation energy eV 1.11 1.11 Si 
0.69 Sbd
0.67 Ge 
Xti Sat.-current temp. exp - 3.0 3.0 jn 
2.0 Sbd
Kf Flicker noise coeff. - 0.  
Af Flicker noise exponent 1. 1.  
Fc Coeff. for forward-bias depletion capacitance formula - 0.5  
BV Reverse breakdown voltage V Infin. 40.
nbv Reverse breakdown emission coefficient - 1. 2.
Ibv Current at breakdown voltage A 1e-10  
Ibvl Low-level reverse breakdown knee current A 0.  
nbvl Low-level reverse breakdown emission coefficient - 1.  
Tnom Parameter measurement temp. °C 27 50
Isr Recombination current parameter A 0.  
Nr Isr emission coeff. - 2  
Ikf High-injection knee current A Infin.  
Tikf Linear Ikf temp coeff. /°C 0.  
Trs1 linear Rs temp coeff. /°C 0.  
Trs2 Quadratic Rs temp coeff. /°C2 0.  
Tbv1 Breakdown voltage temp coeff. /°C 0.  
Tbv2 Quadratic breakdown voltage temp coeff. /°C2 0.  
Tikf Ikf temp coefficient /°C 0.  
Perim Default perimeter m 0.  
Isw Sidewall Is A 0.  
ns Sidewall emission coefficient - 1.  
Rsw Sidewall series resistance Ω 0.  
Cjsw Sidewall Cjo F 0.  
Vjsw Sidewall Vj V Vj  
mjsw Sidewall mj - 0.33  
Fcs Sidewall Fc - Fc  
Vp Soft reverse recovery parameter - 0. .65

The soft reverse recovery parameter, Vp, adds a dQ/dt damping to diode charge as suggested by K.J. Teng and S. Pan in 'Modified charge-control equation for simulation of diode reverse recovery', Electronics Letters, 15th February 1996 Vol. 32 No. 4.

It is possible to annotate a model with voltage and current ratings. This information is displayed in the schematic capture GUI to assist in selecting a device but does not directly impact the electrical behavior in simulation. The following parameters may be specified.

NameDescriptionUnits
Vpk Peak voltage ratingV
Ipk Peak current ratingA
IaveAve current rating A
IrmsRMS current rating A
dissMaximum power dissipation ratingW