PSPice Lab Exercise - Differentiator (Circuit)

  • #1
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Homework Statement:

This is a Lab Exercise, so it's more than one thing. The basic idea is that we need to "build" a Circuit and then examine the Waveforms through PSPice.

Relevant Equations:

Uo = i*R = R*C*[(d*Uc)/(d*t)]
Us = Uc + Uo
Us >>> Uo
Look, this is a weird one, but I really need help. This is the Electronics Laboratory, that is supposed to be hands-on, but with Corona it got cancelled. However, they announced that we'd do it through the internet, had us download PSPice, and now we basically have to try and "translate" the exercise from the leaflets meant for a hands-on approach, to just doing it through this program.

Starting off, we're given this:

Sketch_1.png

The "Us" reads "Frequency Generator". But inside the leaflet, it says that it's a "Source of Square Pulses".

The statement is:

"Draw this circuit in Spice for (α) R=5kΩ, C=2nF & (β) R=250kΩ, C=4nF "
So, we're dealing with two versions where we change the numbers. I get that. My problem is that I cannot find that particular Pulse Generator anywhere in the PSPice library. I also checked my leaflet, and can't find a single example where the circuit is left "open" at the sides (the Uo part). I checked the internet and the program's website, and I'm getting that the generator for square pulses is:

VPULSE.png

Then, the Exercise, says:

"Feed the circuit with Square Pulses of 4Vpp and frequency 0.5kHz."

In my leaflet, I basically have that Vpp is the full voltage between positive and negative peaks of the waveform; that is, the sum of the magnitude of the positive and negative peaks. I get that in the diagrams/waveforms. My question is, what does that mean for the values I'll asign to my "Us"?

Furthermore, as I have no other examples of such circuis, how am I suppose to create that in PSPice? I can do this (disregard the C and R values/names, this is just a quick example:

Circuit.png


How am I supposed to add the "free ends" to the sides? Just add two more wires/buses? Then I suppose I should place the ground. However, as I'm not even sure if that's the correct Pulse Generator, I don't know how to proceed with the values I've been given.

The exercise continues with a second circuit, and I may update with more more info as we continue, but I really need help here just to start this. I know this isn't the exact way we're supposed to upload, but this is the first time I'm doing this, and have no previous experience with the program or how this whole thing works.

Thank you for your time.
 

Answers and Replies

  • #2
Joshy
Gold Member
307
128
Hmm, that's a lot of words and I'm having a difficult time trying to understand your question. Is it: How to set up VPULSE to get square waves or what should you use?

VPULSE.png


I grabbed this from an old lab notes from the university I attended. I would bet my university got it from the cadence support site or maybe the's a help option somewhere. I don't have PSpice on my personal computer so I couldn't check, but I think the above would be sufficiently helpful, yes?
 
  • #3
285
18
Thanks for taking the time to respond. Ultimately I gave up and sent the Professor an email to fail me, and I'll retake the Lab next year. I missed a few classes due to illnesses, and tried taking it without the proper knowledge, so when Corona hit and I couldn't have a "hands on approach" with the actual circuits at University, it became too hard. I called someone who teaches Electronics for some help, but he couldn't understand either, so I threw in the towel. Hey, better to retake it next year and be ready.

I was moving yesterday, which is why it took me too long to respond; apologies. And again, thanks for the taking the time to try this, I appreciate it!
 
  • #4
DaveE
Gold Member
1,122
850
OK, so we don't need to solve your problem until next year. But, a comment about using simulators, which you will want/have to do in the future.

They can be a real PIA to set up. There are a lot of test circuits that you'll have to do just to figure out how to get what you want. So, in this case of a pulse generator with confusing documentation, what I would do is make a circuit with just the generator and a resistor and make measurements to figure out how to get the wave form you want. It is usually less work than wondering if you read the documentation correctly.

Too many people put in a circuit and only measure the output. But then how do you know that you haven't made a mistake? The best way is to build your circuit up piece by piece, gaining confidence with each step that it is correct so far. Later you can skip some steps when you have used the particular simulator enough to be proficient.

Later on when you have a job doing this stuff without someone that has the answers, I think you will find that about 95% of the effort in using simulators is in verifying that you have correctly defined all of the models for your circuit.
 
  • #5
Joshy
Gold Member
307
128
Are you able to audit the class? I would go for it.
 
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