1. 1 Lecture #8 EGR 272 – Circuit Theory II Reference: Read Ch. 1-3 in Schematic Capture Using Cadence PSPICE for general info on PSPICE Read Ch. 5-6 in Schematic Capture Using Cadence PSPICE on AC Sweep and Transient Analysis The following items are available from the instructor or can be obtained from his web page.  PSPICE Assignment Requirements  PSPICE SAMPLE REPORT  AC Analysis - Phasors  AC Analysis - Transients PSPICE Demonstration A demonstration will be performed in class. The following pages highlight some of the key concepts. Also refer to the examples listed above. It is assumed that students already have knowledge of analyzing DC circuits using PSPICE. The focus of this demonstration will be to illustrate the differences when analyzing AC circuits.

2. 2 Lecture #8 EGR 272 – Circuit Theory II Sinusoidal sources - two new types of sources will be introduced for AC circuits: 1)VAC or IAC This source is used for phasor analysis (for finding phasor voltages or currents and also for graphing with frequency on the x-axis in PROBE. The magnitude and angle for the phasor source is specified. This source is typically used with an AC SWEEP analysis. Note that the source does not specify whether it is referenced to a sin or a cos. If you think of the source as a cos source, then the results are also reference to a cos. Part: VACPart: IACPart: VAC with properties changed for a phasor voltage of 100  30 

3. 3 Lecture #8 EGR 272 – Circuit Theory II 2)VSIN or ISIN This source is used for TRANSIENT analysis (graphing sinusoidal waveforms vs time). Specifications are given for max value, DC value, frequency (in Hz), and delay. Note that the source is reference to a sin. Add a delay if it is important to reference to a cos waveform (this is generally not important). Part: VSINPart: ISIN Part: VSIN with properties changed for a time domain voltage of 100sin(2000  t + 30  ) V

4. 4 Lecture #8 EGR 272 – Circuit Theory II Analysis methods - two primary types of analysis are used with AC circuits 1)AC Sweep In this method frequency (in Hz) is varied. This method is typically used with VAC or IAC sources. To analyze at a single frequency, use the same starting and stopping frequency and specify 1 for the number of points (see example below). Include voltage or current printers to display the results in the.OUT file. To generate a graph with frequency on the x-axis in PROBE, use a range of frequencies. The.OUT file may also contain node voltages by default, but these are DC node voltages and are typically equal to zero. Simulation Settings for AC Sweep

5. 5 Lecture #8 EGR 272 – Circuit Theory II 2)TRANSIENT Analysis In this method time is varied. This method is typically used with VSIN or ISIN sources. Specify the range of time values that are to be placed on the x-axis in PROBE (see the sample screen on the next page). Note: AC analysis or Sinusoidal Steady-State Analysis by definition ignores the initial transient response. But PSPICE can only perform a complete analysis, which includes both the transient response and the steady-state response. Therefore, you may see some strange initial behavior when graphing sinusoidal waveforms. If you only want to graph them in their steady-state form, then perform an analysis that is longer than necessary and only view the last portion. For example, if you wish to view the waveforms for 1ms, then you might perform a transient analysis from 0 to 10ms and zoom in on the portion from 9ms to 10ms once in PROBE.

6. 6 Lecture #8 EGR 272 – Circuit Theory II Simulation Settings - Transient Analysis The simulation settings shown below could be used if 5 periods of the waveform 100sin(2000  t + 30  ) V are to be graphed. Note that w = 2000  so f = w/  = 1000 Hz and T = 1/f = 1ms.

7. 7 Lecture #8 EGR 272 – Circuit Theory II Current Printers and Voltage Printers Recall from the analysis of DC circuits using PSPICE that printers are ignored unless: 1)A DC sweep is performed. 2)The DC property is set (such as DC = V(R4) or DC = V(A,B)). Similarly, printers in AC circuits are ignored unless: 1)An AC Sweep is performed. 2)The AC attribute is set (such as AC = VM(L2), indicating the magnitude of the voltage across L2, or AC = IP(C1), indicating the phase (in degrees) of the current through C1). It is also required so specify YES for the properties MAG and PHASE. Sample use of printers in an AC circuit Voltage printer (part VPRINT2) Current printer (part IPRINT)

8. 8 Lecture #8 EGR 272 – Circuit Theory II Current Printers and Voltage Printers Recall from the analysis of DC circuits using PSPICE that printers are ignored unless: 1)A DC sweep is performed. 2)The DC property is set (such as DC = V(R4) or DC = V(A,B)). Similarly, printers in AC circuits are ignored unless: 1)An AC Sweep is performed. 2)The AC attribute is set (such as AC = VM(L2), indicating the magnitude of the voltage across L2, or AC = IP(C1), indicating the phase (in degrees) of the current through C1). It is also required so specify YES for the properties MAG and PHASE. Sample use of printers in an AC circuit