amplifier - Amplify speaker with 9v battery and one transistor

I started electronics recently and I'm trying to make the most basic mp3 amplifier. I try to amplify the music from my phone to the speaker. My phone already amplifies the sound when I connect it directly to the speaker.

I saw that people mostly use lm386 chips but I don't have one yet. So I retrieved some transistors (F3NK80U, J13009) to amplify the sound from the mp3 player to the speaker. My first questions are :

• Are those NPN transistors ?



• Are they suitable for audio ?


• Are they in TO-220 format and the pins in this order : BCE

I read that the base changes the resistance between the collector and the emitter. So should I connect my mp3 player to the base pin, the 9v battery to the collector and the emittor to the ground ?

Finally, what resistance/capacitance should I use ?

Answer

In order of the asking, your three quick questions:

1. From a quick search on alldatasheet.net, the F3NK80 may be a ST made MOSFET, an the J13009 is a Fairchild-made NPN transistor. The last one is along the lines of what you are looking for.


2. Both could be, the J13009 (NPN transistor) a bit more so than the F3NK80 (MOSFET)



3. The J13009 NPN transistor is in a B-C-E orientation, as you can see on this datasheet: https://www.fairchildsemi.com/datasheets/FJ/FJP13009.pdf

And to take a step back, I applaud your effort in putting hardware together to learn electronics. But, I think in this case you are going to need to do a bit more reading, because it will take more than a simple connection of that one transistor to make the amplifier you want. It is a bit like cooking - you have some of the ingredients, but you are going to understand a little more about how it works to BOTH select the other ingredients and use them in a way to give you your dish.

This is why some folks use parts like the LM386 - it is an IC that needs little more than a few parts (which they even tell you the values of on the specification sheet), some power, and connections for your input and output, and you will get a very nice amplifier that shouldn't give trouble. Like here: http://www.ti.com/lit/ds/symlink/lm386.pdf

What you are trying to do is build something a bit like the amplifier that is ALREADY built into the LM386 - which is a great little project - but you are either going to need an existing design like this: http://sci-toys.com/scitoys/scitoys/computers/solderless/amplifier.html or http://myplace.frontier.com/~bwalker1945/1QAFAmp.html

Or learn how to design an amplifier for a selected transistor from the datasheet after understanding how a transistor works. There are so many tutorials, here are a couple: http://www.sentex.ca/~mec1995/tutorial/xtor/xtor1/xtor1.html and http://www.techlib.com/electronics/audioamps.html and a common beginners' electronics book: http://www.amazon.com/Getting-Started-Electronics-Forrest-Mims/dp/0945053282

Any way you go, it'll be something you built yourself. Good luck!