Is it required to memorize all BJT formulas for AC amplification for all BJT configuration and biasing setups?

Am I a failure of an electrical engineer if I don't memorize all of them? They are difficult to memorize because of the several nested fractions. Despite similarities in some configurations, it is still hard to memorize all of them. What do I do?

  • \$\begingroup\$ If you are still in school, of course memorizing will be critical to good grades. But if you forget something in an interview be prepared to at least be able to explain concepts and basic formulas like dc biasing and gain (relevant to almost all configurations). As you become more experienced, you'll be able to derive most equations from simpler, general concepts. Also, there are many engineering roles, some require more memorizing then others (e.g. design vs applications). \$\endgroup\$
    – pat
    Sep 11 at 7:17

You can still be an engineer if you don't memorise all those configurations, and the most important formulae, but you won't be a very good one.

There's always Google, but if you have to look stuff up every time you see a transistor or need to design something with one, then it will take you forever to actually complete anything.

If you don't have a library of common solutions to common problems already in your head, how can you possibly know what approaches exist to solve a particular problem?

I don't think the formulae are as important as the conceptual understanding, but still, you must at least know by heart the basic transistor configurations and some of their variants.

This isn't as difficult as you think. All this comes from experience, and you don't necessarily have to study from dry, boring books. Actually make these things. Try to understand real life circuits. You'll store all this information quite automatically, without having to memorise by repeating some meaningless phrase in your head, over and over, like you do with multiplication tables.

Every time you actually apply some concept, you automatically learn it, and store that knowledge for later. At the very least you'll remember that you did "something like this some time ago" and have an inkling of where to start. You can always look something up, but you have to know what to look up in the first place.

Just apply what you learn. Do exercises, make circuits. Actually use the information, rather than just try to remember it.


Success or failure as an engineer is judged by what you can produce and accomplish, not by what you've memorized. If you need to use equations often, and have trouble memorizing them, print out a cheat sheet and post it at your workstation, or go paperless and bookmark a reference page in your web browser. It's more important that you know how and when to apply the tools of your trade than that you memorize everything. This is true in all fields, not just electrical engineering. Don't stress out about nothing!


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