PSpice Tutorial

          PSpice is a virtual similator for testing electric circuit. A schematic duplication of a circuit can be drawn in the program, and it will analysis the circuit ,thus return feedbacks such as the voltage, currents, and different properties in different components of the circuit. If necessay, it also allows the users to graph the properties of the circuit to study the circuit in depth.

          In this PSpice tutorial, we will be using PSpice to analyze circuits as well as using it to find the thevenin equivalents of a given circuit.

When doing bias point simulation, the information at each node wiould be given,

 

 

          PSpice can also be used to determine  the Thevenin and Norton Equivalents of a circuit. We first test out how to use the program to find thevenin voltage.

We place a imaginary current source alone the load and and set its parameter. Perform a DC sweep on the imaginary current source.

 

Plot the graph with y-axis to be the Voltage of Vout. From the graph, the y-intercept will give the thevenin voltage. From this graph, it shows that the thevenin voltage is 10V.

 

 

          Now, let's try finding the Norton current and the thevenin resistance.

The conventional method is to take off all independent voltage source, and to open the circuit for all indenpendent current sources. From there, you can find the equivilant resister.

 

The alternative is to graph the solution. We place an imaginary voltage source along the load and give its parameter. From there, we do a DC sweep with the imaginary voltage source.

We graph the current alone the load as the y-axis's variable. From the graph, the negative of the slope will be our thevenin resistor and the Norton current is the y-intercept.

 

From the graph:

     slope = (1.5413-3.000)/ 4.8624

              = -3.3

 

     Rth = -slope = 3.3ohm

 

     Inorton= y-intercept = 3A

 

 

 

Detemine Max Power using P-spice.:



Place a imaginary resistor  as the load. Value of the load resistance is set within a parameter.

 

Perform a DC sweep with R5 (load resistor) as the independent variable

 

Graph power vs R4 with power =I(R5)*I(R5)*RL

 

 

 

Trace the Maxima of the graph. At maxima, the power dilivered in at the maximum, and the load resistance is equal to the thevenin resistance of the circuit. From this method, the thevenin resistor is about 3.5 ohm, similar to our previous result.

 

 

From now on, we can use Pspice to confirm our calcuated result in circuit analysis.