The button Change model Reference will allow us to change the model from Dbreak to another model name. Theĭialog box appears with the following items. Using the left mouse button select theĭiode symbol (Symbol should turn red). We must now define the model for the diode. Voltages and currents by using the toolbar button V and I). (In place of Iprobe and Viewpoint you can enable or disable the bias An Iprobe is inserted in the circuit to display the current and a Viewpoint is used to obtain We construct the following schematic using the part Dbreak for the diode. The diode parameters are I S = 2.6 x 10 -15 A, V T = 26mV, and n = 1. The supply voltage is 2 V, and the current limiting resistor R 1 = 1KW. Use PSpice to find the diode current and voltage in the circuit shown To run the examples, students can download the complete Free OrCAD Software for Students. To view the Pspice examples you need to download the OrCAD Viewer Free Download.
Usually only need to specify the saturation current, I S (PSpice default is I S = 10 -15 A).ĭownload PSPICE Schematic Files for EE-253. The thermal voltage, V T, is approximately 26 mV at room temperature, so we The basic low frequency diode current-voltage relationship is given by The diode is a two terminal device that essentially allows current conduction in only You only need to specify those parameter values that are different than the default values.
In essence, PSpice has built-in generic models for semiconductor devices.
PSpice contains default values for all parameters. with many parameters, it is often not necessary to explicitly list all of them. Although PSpice allows the user to describe diodes, BJTs, etc. Only one model definition is then needed. Therefore, if there are two or more of the same diodes in a circuit, each diode circuit description statement uses the same model name.
A separate model definition lists the device parameters. The circuit statement gives the device, the nodes that are connected to, and a model name. For these reasons, semiconductor devices are described with two statements. For example, the diode model in PSpice has 14 parameters, while the BJT model has 40 parameters! In addition, many electronic circuits contain several of the same diodes or transistors. However, semiconductors are usually described with many parameters. The resistor, capacitor, and inductor are each adequately described with a single parameter. Please refer to a PSpice manual for full details on these and other semiconductor devices and circuits. We discuss here only very simple models for the diode and BJT. PSpice allows the user to model semiconductor devices such as diodes, bipolar junction transistors (BJT), field effect transistors, and integrated circuits such as operational amplifiers.
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