diode :
A diode circuit element.

The diode primitive represents a two-terminal diode. Note that this primitive is a pseudo-module to describe a structural netlist of electrical circuits and not a behavioral model by itself. The XMODEL simulator extracts an event-driven behavioral model at run-time based on the circuit network described by these circuit-level pseudo-modules.

The diode primitive can model diodes in three ways: using an ideal model (ideal), exponential model (exp), or piecewise-linear model (pwl).

1) Ideal diode model (model = ‘ideal’)

The diode turns on when the voltage across the two terminals (pos and neg) is higher than the specified turn-on voltage (Von) and turns off otherwise. The parameters Ron and Roff define the turn-on and turn-off resistances, respectively.

2) Exponential diode model (model = ‘exp’)

The diode current (Id) is an exponential function of the voltage (Vd = V(pos) – V(neg)) according to the following equation:

    Id = Is * (exp((Vd-Id*Rs)/(N*VT)) - 1)
    where VT = kT/q (25.695mV at 25C)

In this equation, Is and VT change with the global parameter `global_temp, defining the temperature in Celsius (default: 25C). Specifically, the thermal voltage VT is proportional to the absolute temperature and the transport saturation current Is is proportional to exp(-VG0/VT), where VG0 is assumed to be 1.205V for silicon.

The parameters abstol and reltol set the error tolerance approximating these equations.

3) Piecewise-linear diode model (model = ‘pwl’)

Using this model, the diode can have an arbitrary piecewise-linear I-V characteristic. In this case, the diode is equivalent to a nonlinear resistor (the res_var primitive). The parameter R_data describes the piecewise-constant resistance values across different voltage intervals, using the same format as the R parameter in the res_var primitive.

For all the diode models, the parameter C defines the linear capacitance across the terminals and the parameters Cpos and Cneg define the linear capacitance of the terminals pos and neg to the ground, respectively.

Input/Output Terminals

Name	I/O	Type	Description
pos	input	xreal	positive terminal
neg	input	xreal	negative terminal

Parameters

Name	Type	Default	Unit	Description
model	string	“ideal”	None	diode model
Von	real	0.0	volts	turn-on voltage
Ron	real	0.01	volts	turn-on resistance
Roff	real	`INFINITY	volts	turn-off resistance
Is	real	1e-16	ampere	saturation current
N	real	1.0	None	emission coefficient
Rs	real	0.0	ohms	series resistance
abstol	real	1e-9	A	absolute tolerance
reltol	real	0.1	None	relative tolerance
R_data	real array	‘{1.0}	ohms	PWC resistance
C	real	0.0	farads	pos-to-neg capacitance
Cpos	real	0.0	farads	pos-to-gnd capacitance
Cneg	real	0.0	farads	neg-to-gnd capacitance
m	real	1.0	None	multiplicity factor