===More on Shared Models===
Most active devices like a diode or a transistor have a set of shared model [[parameters]] and a model name that identifies that set of shared model parameters. If you add two default bipolar junction transistors to a circuit, then by default, they will share the same model and model [[parameters]]. With shared models, the varying parameters will share the same value even though they belong to more than one part. For example, if your circuit has two bipolar junction transistors that share the same model, and if you set the tolerance of the "bf" parameter to 5% and its value to 100, and then you run a Monte Carlo DC Bias test (operating point analysis), the two transistors will have identical bf’s for each iteration of the Monte Carlo analysis.
There is a way to prevent models from being shared when you create them. Open the Schematic Options Dialog from the Edit Menu of the Schematic Editor, then go to its General page/tab and Check the checkbox labeled “New devices have unique models” at the top of the page. Once a part is placed, there is also a way to make it unique. Double-click on the part's symbol to open its property dialog, then click on the “Make Model Unique” button. The model will be made unique if it was previously shared. Resistors, capacitors, and inductors are special cases. With these types of devices do not share model [[parameters]] as you place them in the circuit. However, the semiconductor or temperature-dependent versions of these devices do share models and behave like transistors as discussed above.
===Tying Up Parameter Tolerances===