Symbol Names: DIODE, ZENER, SCHOTTKY, VARACTOR.
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=1e10)
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 regionwise 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 nonlinear 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 IV 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:
Name 
Description 
Units 
Default 
Ron 
Resistance in forward conduction 
W 
1. 
Roff 
Resistance when off 
W 
1./Gmin 
Vfwd 
Forward threshold voltage to enter conduction 
V 
0. 
Vrev 
Reverse breakdown voltage 
V 
Infin. 
Rrev 
Breakdown impedance 
W 
Ron 
Ilimit 
Forward current limit 
A 
Infin. 
Revilimit 
Reverse current limit 
A 
Infin. 
Epsilon 
Width of quadratic region 
V 
0. 
Revepsilon 
Width of reverse quad. region 
V 
0. 
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 
1e14 
1e7 
Rs 
Ohmic resistance 
W 
0. 
10. 
N 
Emission coefficient 
 
1 
1. 
Tt 
Transittime 
sec 
0. 
2n 
Cjo 
Zerobias 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 forwardbias depletion capacitance formula 
 
0.5 

BV 
Reverse breakdown voltage 
V 
Infin. 
40. 
Ibv 
Current at breakdown voltage 
A 
1e10 

Tnom 
Parameter measurement temp. 
ºC 
27 
50 
Isr 
Recombination current parameter 
A 
0 

Nr 
Isr emission coeff. 
 
2 

Ikf 
Highinjection knee current 
A 
Infin. 

Tikf 
Linear Ikf temp coeff. 
/ºC 
0 

Trs1 
linear Rs temp coeff. 
/ºC 
0 

Trs2 
Quadratic Rs temp coeff. 
/ºC/ºC 
0 

It is possible to specify voltage, current, and power dissipation ratings for a model. These model parameters do not affect the electrical behavior. They allow LTspice to check if the diode is being used beyond its rated capability. The following parameters apply to either model. These parameters do not scale with area.
Name 
Description 
Units 
Vpk 
Peak voltage rating 
V 
Ipk 
Peak current rating 
A 
Iave 
Ave current rating 
A 
Irms 
RMS current rating 
A 
diss 
Maximum power dissipation rating 
W 