Daniel.Can the OrCAD PSpice model for LM7815 be modified to simulate LM7824?

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Discussion Overview

The discussion revolves around the possibility of modifying an OrCAD PSpice model for the LM7815 voltage regulator to simulate the LM7824. Participants explore the technical aspects of this modification, as well as the relevance and utility of using simulation software for common voltage regulators.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes that the LM7815 and LM7824 are similar linear regulators, suggesting that the output voltage setting is the primary difference, and proposes modifying the voltage divider in the 7815 model to achieve 24V.
  • Another participant expresses skepticism about the necessity of simulating a common voltage regulator, advocating for hands-on circuit design instead and emphasizing the importance of understanding circuit diagrams.
  • A later reply agrees with the skepticism but mentions that the simulation is required for a project as mandated by a teacher, highlighting the constraints faced by students.
  • One participant shares their experience of not relying on simulation programs for analog circuit design until more complex scenarios arise, suggesting that practical understanding is more beneficial.
  • Another participant mentions attempting to modify the PSpice model but has not achieved useful results yet.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and utility of using PSpice for common voltage regulators. While some suggest it is a straightforward modification, others question the value of simulation in this context. The discussion remains unresolved regarding the best approach to take.

Contextual Notes

Participants highlight limitations in their understanding of the PSpice model modification process and the constraints imposed by educational requirements. There are also references to the complexity of circuit design and the varying levels of reliance on simulation tools.

djrama
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Hello!

My version of OrCAD (16.0) doesn't have a pspice model for the 7824 regulator... I was searching in google for information but I haven't found anything useful.

Maybe modifying 7815 model (which I already have) or something, but I don't know how to do this.

Any help would be appreciated!

Thanks.
Daniel.
 
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djrama said:
Hello!

My version of OrCAD (16.0) doesn't have a pspice model for the 7824 regulator... I was searching in google for information but I haven't found anything useful.

Maybe modifying 7815 model (which I already have) or something, but I don't know how to do this.

Any help would be appreciated!

Thanks.
Daniel.

Welcome to the PF.

I think those are just jellybean linear regulators, so the difference is just the output voltage setting, right? You should be able to figure out where the voltage divider/setting circuit is in the 7815 regulator model, and just change the divider to give you 24V.
 
May I make a suggestion?

Why even do any pspice on a common voltage regulator? Do it on circuit you design!

I have to say, don't get too depend on any simulation program. I take that you are a student, learn to look at the circuit diagram of 7824/78xx and learn how it work. You don't get insight using pspice at all. I can tell you in my 30 years of career doing heavy duty analog circuit design, I never use any simulation program until RF. I only use Microwave Office because of the complexity of the circuit model with all the parasitic components and also at the speed that speed of light become an issue and signals has to be represented as phasors and traveling waves. Also the Smith Chart is not exactly intuitive. In fact Microwave Office help me start thinking in Smith Chart, how the circuits dancing on the Smith Chart!:smile:

It is like with all the GPS and cell phone with memory and intelligence, I still try to remember phone number and remember the direction and look up maps. One day if there's an EMP pulse, people will be totally loss!

If you want to learn pspice, design an op-amp ( transistor level) then do the simulation. Or start out with a single stage transistor and to differential pair, then current mirror and then add them together. Verify Bode Plot along the way. Don't think those circuits are that complicated. Learn to break them apart into building blocks and it is very easy to understand.

Just a thought
 
Last edited:
yungman said:
May I make a suggestion?

Why even do any pspice on a common voltage regulator? Do it on circuit you design!

I have to say, don't get too depend on any simulation program.

Absolutelly right, and yes, in my previous university courses I have learn about calculations in several electronics circuits (maths, maths, maths...) but in this case, the problems cames by the teacher who wants to have the pspice simulation of the whole project, not only the 7824.

Thanks for the reply!
 
berkeman said:
Welcome to the PF.

I think those are just jellybean linear regulators, so the difference is just the output voltage setting, right? You should be able to figure out where the voltage divider/setting circuit is in the 7815 regulator model, and just change the divider to give you 24V.

I was messing around with the pspice model but at this point I haven't get any useful result.

Thanks for the reply!
 

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