Troubleshooting PSpice Schematic: VDC=10V

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Discussion Overview

The discussion revolves around troubleshooting a PSpice simulation issue involving a schematic with a DC voltage source, resistor, and capacitor in series. Participants are exploring the expected output of the simulation and the reasons for obtaining a constant voltage reading instead of a transient response.

Discussion Character

  • Technical explanation, Debate/contested, Experimental/applied

Main Points Raised

  • One participant reports that the simulation yields a straight line at 10V instead of a curve from 0 to 10V, indicating a potential issue with the setup.
  • Another participant suggests that the issue may stem from performing a bias-point simulation instead of a transient simulation and recommends using a step source instead of a VDC source.
  • A participant expresses confidence that they are conducting a transient simulation, as indicated in the simulation profile, and questions the necessity of using a step source over VDC.
  • Another contributor notes that while DC is acceptable, the program might calculate the initial bias point, which could be the same as the final output, and suggests using a step DC or a switch with an appropriate time step.
  • One participant agrees with the previous suggestion and emphasizes the importance of ensuring the time scale is small enough to capture the transient response accurately.

Areas of Agreement / Disagreement

Participants express differing views on whether a step source is necessary and the implications of the time scale on the simulation results. The discussion remains unresolved regarding the best approach to achieve the expected transient response.

Contextual Notes

There are limitations regarding the assumptions about the simulation setup, the definitions of the sources used, and the time scale settings that may affect the output. Participants have not reached a consensus on the optimal configuration for the simulation.

david90
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In my schematic, i have vdc = 10v, a resitor,ground and a capcitor. All 3 are in series except ground. When I run simulation, I get a straight line at 10v instead of a curve from 0 to 10v. I put the voltage probe between resistor and cap btw.
 
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You're probably doing a bias-point simulation instead of a transient simulation. You might also want to try using a step source instead of VDC source.

- Warren
 
i'm pretty sure I'm doing a transient simulation because in the sim profile it says so.

Is it necessary to use a step source instead of vdc? On my worksheet that my teach gave me, it shows vdc.
 
Dc is okay , but the program may calc the initial bias point which may be the same as your final. ( skip this if you can ) . other wise use a step dc. or a switch . Make sure you time step is small enough so it makes sense . Pspice is almost always correct but the setup is usually the problem. Ray.
 
time scale

I think rayjohn may be on to somehting there - make sure your time scale is small enough.

For instance, if your circuit has a time constant of 10us and you simulate it for 10s, the response over the full simulation time will likely look like a steady 10V.
 

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