The Transistors library is one of the component library types within the Component Library included in PI Expert.. Once a silicon controlled rectifier is added to the library and included in a Component Set, you can manually choose your custom transistor to be used where applicable. Transistors are currently used as switches to activate a protection feature within a Power Integrations IC (e.g. secondary overvoltage protection for LinkSwitch-PH).
PI Expert does not allow you to modify or delete the default components. You can only view the parameters of a selected component type by clicking the View button. You can add custom components to the Component Library by clicking the Add button in the Component Library dialog where you can input all relevant specifications for a particular component. See the Component Library topic for more information on adding and editing components.
You can specify the following transistor parameters:
Type - Transistor type
Mfg. Part# - Transistor manufacture part number
VCE - Maximum collector-emitter voltage in volts ( V)
IC Cont - Maximum continuous collector current in milli-Amps (mA)
Power - Maximum power dissipation in milli-Watts (mW)
The following settings are common to all component type parameter dialogs:
Manufacturer - The name of the company that manufactures the component.
Part Number- The part number that uniquely identifies the component.
Click OK to add the silicon controlled rectifiers to the library. The 
User mark will indicate the custom transistor in the list.