I am trying to run a simple Op Amp simulation. My lab gives zero instruction on PSpice, tossed us a brief manual on DC PSpice circuits (even though the class is AC), and said go forth. The circuit I am trying to build is below:

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The values for components are: R1 = 330 Ω. R2 = 6800 Ω. R3 = 2200 Ω. C1 = 0.01uF

The amplitude of Vi = 5V, and the frequency of Vi = 1000Hz.

I expect around 20V at the output V2.

My PSpice Circuit is below:

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I create a blank new project. I build the circuit. I create simulation profile. When I run the simulation, The output shows a constant 0 V. Output below:

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Does anyone know where I might be going wrong, in the setup or the circuit?

EDIT: New circuit schematic below after changing setting from transient to AC Sweep/Noise:

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New simulation:

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  • \$\begingroup\$ Can you get the actual SPICE netlist from PSpice? Also it looks like you did a transient simulation rather than an AC simulation. Is that what you intended? \$\endgroup\$ – The Photon Mar 10 '19 at 19:51
  • \$\begingroup\$ @ThePhoton I changed my source to a different component that specified the frequency, and I got a new output (sin-looking but still funky). I want to see the magnitude of the output voltage (and the phase if possible). Not sure about the differences between transient and AC sims. I shall edit my post to reflect the changes, and I will post the netlist if I can find it. \$\endgroup\$ – Mr.Mips Mar 10 '19 at 19:55

First, the answers to this question will help you understand what's going on:

How do Circuit Simulators actually work?

Short version, as applied to your problem: SPICE supports several types of analysis. Two of these are transient and AC analysis. The AC analysis linearizes the circuit and tells you how it will respond to small AC signals around a fixed bias point. The transient analysis will also include nonlinear and start-up effects. The AC analysis might fit your problem better because it will allow you to sweep the frequency of the stimulus, and also it usually runs faster than a transient analysis.

Most importantly to your question, an AC source won't produce any signal in a transient simulation and a time-domain source won't produce any signal in an AC simulation. You were using an AC source in a transient simulation, so you didn't see any signal.

  • \$\begingroup\$ Got it. I changed the simulation profile settings to AC Sweep/Noise. Start freq is 1, end freq is 100000. Points per decade is 10. In my edited simulation, I'm getting a constant V output just over 1 V that slopes down after awhile. I expect about 20 V magnitude at the output. Do you believe this is an issue with my circuit, or with the settings still? \$\endgroup\$ – Mr.Mips Mar 10 '19 at 20:39
  • \$\begingroup\$ @Mr.Mips: Looking at you 'new' schematic and the waveform, you are still using the vsin source with the AC analysis? \$\endgroup\$ – Linkyyy Mar 10 '19 at 22:31
  • \$\begingroup\$ @Linkyyy The vsin source is the correct one, no? It's a sinusoidal V source, so shouldn't vsin be the source? Or should I use the previous source I had originally used? \$\endgroup\$ – Mr.Mips Mar 10 '19 at 22:45
  • \$\begingroup\$ @Mr.Mips, a sinusoidal time domain source is not the same as an ac source. That's the point of my answer. Unfortunately I don't know how these are named in the PSpice GUI editor. \$\endgroup\$ – The Photon Mar 10 '19 at 23:05
  • \$\begingroup\$ "vsin" are for time domain simulations, "vac" is for AC analysis. \$\endgroup\$ – Linkyyy Mar 11 '19 at 12:27

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