Diode Characteristics Curve

I am trying to model diode characteristic curve, But cannot simmulate the knee voltage, or the breakdown voltage.

Is it possible to do so?

I am using the Student version.

regards waqar shahid

by waqarshahid
August 18, 2014

Here is the link to my circuit


by waqarshahid
August 18, 2014

I'm not the best with diodes. For starters I don't think CL dose break down voltage, which I can understand because it may have different unpredictable characteristics after being in that region. But I could get a 'Knee voltage' when I simulated your circuit from -1V to 3V with a step size of 0.01V.

by Garrett
August 19, 2014

Yes, knee voltage is OK


by waqarshahid
August 19, 2014

Garrett is right; CL does not model reverse breakdown voltage.

Most vendor-supplied spice models for simple diodes include a reverse breakdown voltage parameter (BV) but CL is not a spice simulator and, as already mentioned, does not support the BV parameter so reverse breakdown cannot be modelled directly in a CL diode.

For a bit more background to CL's diode models ...



and ...

About datasheet, device and simulation model parameters

SPICE parameters for devices have little to do with datasheet specifications. They are much more to do with semiconductor physics and the particular process under which a given device is manufactured at the foundry. Consequently it is not always a simple task to map datasheet information onto the model parameters.

So ... what you can do is trawl manufacturers websites for a diode spice model for your target diode

From there you pilfer the parameters that you can use in the CL model and set up the CL model using them (Edit parameters > Edit individual parameters).

In the background, build a diode test jig like the one in this lively little thread:


to sanity check your CL diode against its original datasheet.

If you want to try to understand more about what the SPICE - and hence CL - parameters mean in diodes, bipolar transistors and MOSFETs, then you might like to have a look at:


with individual slide sets:




For more detailed information about bjt's in particular, have a look at this book:


available from:




Another excellent (and free) book about transistor modelling, go to:


and register to get a copy of:

Definitive Handbook of Transistor Modeling

However, if you can find a spice model for your target device, then you can edit the relevant parameters of one of the built-in CL models and use that in your circuit.

For more information please see this thread:


Note that there are some unanswered questions about editing CL model parameters (which may not affect you anyway):


This thread has several links to more about spice diode parameters:


by signality
August 21, 2014

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