general purpose transistor for audio

Thread Starter


Joined Sep 6, 2010
I've been working through the projects in the Make: Electronics book. Up to this point, the only transistor used in all the projects is the 2N2222. It's often used to drive a small speaker in the siren/noise-maker circuits in this book. Sometimes two 2N2222s are connected 'in series' to drive the wouldn't be enough as the book explains.

What is a good alternative the the 2N2222, but offering higher current potential to properly drive a small or midsize speaker with only one transistor? It doesn't matter if it's a bit larger in size. It must be NPN and 3 terminals...used just like the 2N2222, as well as very easy to find. It will be used in battery-powered circuits of 9V or less. Forgive the basic-ness of this question.


Joined Aug 1, 2013
There are several intermediate transistor package sizes between TO-18/TO-92 and TO-220, but the TIP-31 transistor is hard to beat for cost, availability, and reputation. The three pins are not in the same order and the gain is slightly less, but it is an excellent "big brother" to the 2222, 3904, and 4401 small signal parts in almost all applications. For the same 60 V collector rating you want the TIP31A.

Warning: The collector is connected to both pin 2 (center) and the mounting tab.