Need Help Finding Simple, Succinct Transistor Tutorial

[Rory Starkweather]

I want to write a simple VB6 program to model transistor function. At this point, one transistor at a time and DC. (This is my first attempt.)

I have seen a number of web based apps, and I don't like any I have seen.

I want to build something that works, largely, in a manner that provides a comfortable interface, for the user, and accurate results. Well, as accurate as electronic fairyworld allows.

I DON'T want to compete with LTSpice. I just want to create something that can be used, quickly, easily, and locally, to see what one transistor will do under certain conditions.

As I said, I'm looking for a tutorial that I can plagiarize to create the app. I don't want any extra hogwash about electrons and their environment, or the difference between a P layer and an N layer. I will assume that people who use the app will know the difference.

Does anyone have any useful links?

 

[(*steve*)]

This is hard to answer, mostly because spice doesn't necessarily use a complex model for a transistor. The hard part is modelling all the other current flows in a circuit -- each element is relatively simple.

I would look to see what some spice program uses.

If you want something really simple, one might ask how well you want to model (say) the base-emitter junction. Are you happy with it being treated as an almost perfect diode (just having a fixed forward voltage drop), or do you want to model its V vs I behaviour? For the collector-emitter path, you have similar things to consider. There are three normal regions of operation (cutoff, linear, and saturation). How well do you want to model each, and what about the transition of one to another?

Ironically, I think the more complex models will make your software easier to use by virtue of it being more "plug and play" and operating over the widest range of conditions. However, the more complex models will require you to define more and more characteristics.

 

[Rory Starkweather]

Thank you very much. I intend to start with a basic BJT. The formulae are well known, but I have forgotten them.

I don't want to use Spice. I want this to be an 'enclosed' application.

But your response interests me. I don't plan on including AC applications, so I am wondering what effect the rest of the circuit could have.

I have no problem with adding individual transistor types to it. That's a great idea. Requires about 10 minutes of programming. Allowing users to add more, or different data will take a little longer, but is still a really good idea.

 

[(*steve*)]

I didn't suggest you use spice, but google the model used in spice! (see here).

Or simply google for general transistor models. (or just see here for a list of several models).

 

[Rory Starkweather]

That is exactly what I needed. TYVM.