LTspice: Simple Idealized Diode

LTspice semiconductor diode models are essential for simulations, especially when you want to see results that include breakdown behavior and recombination current. However, as complete as the semiconductor diode model is in LTspice, there are times when you need a simple “idealized diode” model to quickly simulate, for example, an active load, a current source or a current limiting diode. To assist, LTspice provides a representation of an idealized diode model.

To use of this idealized model in LTspice, insert a .model statement for a diode (D) with a unique name and define one or more of the following parameters: Ron, Roff, Vfwd, Vrev or Rrev.

.model MyIdealDiode D(Ron=1 Roff=1Meg Vfwd=1 Vrev=2)

The idealized diode model in LTspice has three linear regions of conduction: on, off and reverse breakdown. The forward conduction and reverse breakdown can further be specified with current limit parameters Ilimit and revIlimit.

.model MyIdealDiode D(Ron=1 Roff=1Meg Vfwd=1 Vrev=2 Ilimit=1 RevIlimit=1

Furthermore, to smooth the switch between the off and conducting states the parameters epsilon and revepsilon can also be defined.

.model MyIdealDiode D(Ron=1 Roff=1Meg Vfwd=1 Vrev=2 Ilimit=1 RevIlimit=1 Epsilon=1 RevEpsilon=1)

Ideal Diode Schematic

A quadratic function is also used between the off and on state such that the idealized diode IV curve is continuous in value and slope, so that the transition occurs over a voltage specified by the value of epsilon and revepsilon.

Once you have inserted your .model statement in your schematic you can edit the diode symbol’s Value in the component attributes (Ctrl + Right Click) to match the name you specified in your statement. For more information on LTspice diode models, please refer to the help topics (F1).

Ideal Diode Waveform

Just for fun, in the circuit example below an idealized diode model is used to simulate a MOSFET’s RDS(ON) in an otherwise nonsynchronous step-down controller. By using an idealized diode model instead of the traditional Schottky diode, the conduction losses of synchronous rectification can be easily compared.

Ideal Diode Example



Gabino Alonso

Gabino Alonso目前是Power by Linear™部门的战略营销总监。加入ADI公司之前,Gabino在凌力尔特、德州仪器、加州理工州立大学担任过市场营销、工程、运营和讲师等多个职位。他拥有加州大学圣巴巴拉分校电子和计算机工程硕士学位。