Spice Model

If the component has no spice model can you create it on your own? and is it readable in NGSpice?

It is possible - most simulators (should) support the basic SPICE model syntax. That said, accuracy of models depends on the correctness and amount of parameters that are entered into the model file or code (especially for semiconductors). So yes, you can write your own SPICE models but they might not be accurate.

do you have a format on how to do it?

This is the 3055 BJT model that I cooked up using an existing power transistor model and tweaking it:


[code line="none"].model MJ3055 npn ( IS=2.37E-13 VAF=200.0 BF=90 IKF=1.8495 NE=1.5319
+ ISE=2.876E-11 IKR=0.1 ISC=1.00E-09 NC=1.5 NR=1 BR=10 RC=0.05 CJC=6.00E-10
+ FC=0.5 MJC=0.33 VJC=0.5 CJE=3.50E-09 MJE=0.5 VJE=1.5 TF=2.20E-08
+ ITF=10 VTF=5 XTF=5 RE=0.03 TR=4.40E-06)[/code]

You need to save it in a file with extension as per the model files extension recognised by the simulator.

NOTE: There is no guarantee that the model is accurate - however all simulations that I have done using it seem to be fine.

For components that cannot be modelled directly as above, you can model them as combination of simpler "constituent" components of the device (for example a BJT modelled as a combination of two diode models), but this will generally not be as accurate.

tnx., for the help., i tried it and it work., im looking for more rare components like MESFET do you have any? even any manufacturer?

I do not know of any MESFET model. As I said earlier, if no model is available then you have to refer to the device's equivalent circuit (like the way BJTs are represented as two back-to-back diodes or SCRs are represented as a combination of a PNP-NPN pair) and then make up a sub-circuit or model based on the components in the equivalent circuit.

copy that tnx