D. Diode

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=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 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 1e-14 1e-7 Rs Ohmic resistance W 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. Ibv Current at breakdown voltage A 1e-10 Tnom Parameter measurement temp. ºC 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. /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