PSpice User's Guide
Contents
1. i i B 7 E EEEE yo iek y re H D i i iia 1 i f 1 i 1 i H I i H 1 i t H ia i 1 I OOo SS 1 a a 1 1 1 1 va ha H f A1 166 666H 35 776 ss i i A2 166 666 17 874 dif 166 606H paaa ee ee ar a ee a a a aa aaa a aaa aa a A Figure 25 Small signal frequency response at 100 and 10 kQ input resistance Note that the Y value for cursor 2 in the cursor box is about 17 87 This indicates that when R1 is set to 10 kQ the small signal attenuation of the circuit at 100Hz is 17 87dB greater than when R1 is 1002 6 From the Trace menu point to Cursor and choose Display to turn off the display of the cursors Delete the trace Finding out more about parametric analysis To find out more about this See this parametric analysis Parametric analysis on age 12 382 using global parameters Using global parameters and expressions for values on page 3 107 Parametric analysis 892. Chapter 2 Simulation examples 84 Not in A Basics Parametric analysis This example shows the effect of varying input resistance on the bandwidth and gain of the clipper circuit by e Changing the value of R1 to the expression Rval e Placing a PARAM part to declare the parameter Rval e Setting up and running a parametric analysis to step the value of R1 using Rval CH OAhrso40 Feval Ce D1 M2940 Figure 22 Clipper circuit with global parameter Rval This example produces multiple analysis runs each with a different value of R1 After the analysis is complete you can analyze curve families for the analysis runs using PSpice A D Setting up and running the parametric analysis To change the value of RI to the expression Rval l 2 3 4 In Capture open CLIPPER OPJ Double click the value 1k of part R1 to display the Display Properties dialog box In the Value text box replace 1k with Rva1 Click OK To add a PARAM part to declare the parameter Rval l 2 From Capture s Place menu choose Part In the Part text box type PARAM from the PSpice library SPECIAL OLB then click OK Place one PARAM part in any open area on the schematic page Double click the PARAM part to display the Parts spreadsheet then click New In the Property Name text box enter Rva no curly braces then click OK This creates a new property for the PARAM part as shown by the new column la
3. ameter value for each You can select one or more runs to display To display all 21 traces Inthe Available Sections dialog box click OK To select individual runs click each one separately All 21 traces the entire family of curves for VDB Out appear in the Probe window as shown in Figure 24 To see more information about the section that produced a specific trace double click the corresponding symbol in the legend below the x axis I 1 504 7 4 p 7 2 2 5 4 5 5 2 5 l 10Hz 180Hz 1 OKHz 10KHz 406KHz 1 OMHZ 18MHz 100MHz 4 0GHz oe VF AOFXAY KOOFAOHXAY KO UDB Out Figure 24 Small signal response as R1 is varied from 100Q to 10 kQ 2 Click the trace name to select it then press to You can also remove the traces by remove the traces shown removing the VDB marker from your schematic page in Capture 87 Chapter 2 Simulation examples press or You can avoid some of the typing for the Trace Expression text box by selecting V OUT twice in the trace list and inserting text where appropriate in the resulting Trace Expression press or The search command tells PSpice to search for the point on the trace where the x axis value is 100 88 To compare the last run to the first run From the Trace menu choose Add Trace to display the Add Traces dialog box 2 Inthe Trace Expressio
4. beled Rval in the spreadsheet Click in the cell below the Rval column and enter 1k as the initial value of the parametric sweep While this cell is still selected click Display In the Display Format frame select Name and Value then click OK Click Apply to update all the changes to the PARAM part Close the Parts spreadsheet Select the VP marker and press to remove the marker from the schematic page From the File menu choose Save to save the design Parametric analysis PSpice interprets text in curly braces as an expression that evaluates to a numerical value This example uses the simplest form of an expression a constant The value of RI will take on the value of the Rval parameter whatever it may be Note For more information about using the Parts spreadsheet see the Orcad Capture User s Guide This example is only interested in the magnitude of the response 85 Chapter 2 Simulation examples The root schematic listed is the schematic page associated with the simulation profile you are creating This profile specifies that the parameter Rval is to be stepped from 100 to 10k logarithmically with a resolution of 10 points per decade The analysis is run for each value of Rval Because the value of R1 is defined as Rval the analysis is run for each value of R1 as it logarithmically increases from 1002 to 10 kQ in 20 steps resulting in a total of 21 runs gt 86 To set up and r
5. n text box type the following Vdb Out 1 Vdb Out 21 3 Click OK Note The difference in gain is apparent You can also plot the difference of the waveforms for runs 21 and 1 then use the search commands to find certain characteristics of the difference 4 Plot the new trace by specifying a waveform expression a From the Trace menu choose Add Trace b Inthe Trace Expression text box type the following waveform expression Vdb Out 1 Vdb OUT 21 Click OK 3 Use the search commands to find the value of the difference trace at its maximum and at a specific frequency a From the Trace menu point to Cursor and choose Display b Right click then left click the trace part triangle for Vdb Out 1 Vdb Out 21 Make sure that you left click last to make cursor 1 the active cursor From the Trace menu point to Cursor and choose Max d From the Trace menu point to Cursor and choose Search Commands e Inthe Search Command text box type the following Search forward x value 100 f Select 2 as the Cursor to Move option g Click OK Figure 25 shows the Probe window with cursors placed 1 H 1 i 1 3 i i 1 7 1 i 1 i I ai OE 1 J 1 1 H H i 5 1 i 1 p 1 i 1 i 1 i j H 1 A F P es EET ETETE a NW errero rr rrr e r A Y ore ssereserrererrerererereeeeeseserrerererssesses 1 i i 1 i i i 1 i 1 i 1 J i j H 1
6. un a parametric analysis to step the value of R1 using Rval l From Capture s PSpice menu choose New Simulation Profile The New Simulation dialog box appears In the Name text box type Parametric From the Inherit From list select AC Sweep then click Create The Simulation Settings dialog box appears Click the Analysis tab Under Options select Parametric Sweep and enter the settings as shown below Simulation Settings Parametric General Analysis Include Files Libraries Stimulus Options Data Collection Probe Windows Analysis type Sweep variable ac Sweep H ose Voltage source Hame Curent source Options Model type i General Settings L Monte CarloWforst Case fa Parametric Sweep Temperature Sweep Save Bias Point Load Bias Point Be Start value i oO f Ok End value Logarithmic Decade z Points Decade i 0 Value list i Global parameter Model name Model parameter Temperature Parameter name Rival Sweep type Cancel Apply Help Figure 23 Parametric simulation settings 6 Click OK From the PSpice menu choose Run to start the analysis Parametric analysis Analyzing waveform families Continuing from the example above there are 21 analysis runs each with a different value of R1 After PSpice completes the simulation the Available Sections dialog box appears listing all 21 runs and the Rval par
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