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[on:]

I have to believe this has been covered before but I can't find what I'm looking for using the site search engine so I apologize if this is a recent repeat.

I don't need quality sound for my toy project and I don't want to connect a speaker directly to my Arduino. I'm looking for a cheap radio shack or grab bag parts type single transistor amplifier circuit recommendation. Maybe a 2n2222 circuit. I have 9 volts available and a 16 ohm speaker.

I'm also not opposed to learning how I can design a simple transistor amplifier circuit for myself.

A link would be great.

Thanks - ddm

[Reply #1 on:]

Google is your friend. There is loads of info on simple transistor audio amps.

A simple single transistor pre-amp is at http://hackaweek.com/hacks/?p=327

EDIT: If you do follow the hackaweek desig to build a preamp and LM386 amplifier them bear in mind you don't need resistor R1 shown in the circuit at the above link. You only need a transistor, 2 caps and 2 resistors to make a simple audio amp.

Try googling for '2 transistor 1 watt amplifier' as that will probably be better for your project.

OR you could buy a cheap audio amp IC for your project. Small ones of a couple of watts can be had for pennies. You can get higher powered stero amp IC's of 25Watts for £2-£4.

[Reply #2 on:]

As is usual for me, my question was poorly worded. It should have been, "Can I use any single transistor audio amplifier on my Arduino, even if I'm only amplifying (more like isolating) a 5 volt signal to 9 volts because all I can find with a Bing search are tiny signal audio amplifiers. If not, is there a Recommendation for a single transistor audio amplifier circuit?"

I believe you answered to the affirmative.

thanks - that's all I needed to know.

[Reply #3 on:]

A minimal amp needs two resistors: from power supply to the collector (1k - 10k) and from collector to the base (100k or over). You may need two capacitors on the base and collector. The signal is applied to the base and output on the collector. emitter grounded.

Fairly stable bias.

[Reply #4 on:]

Because audio is such an extremely minor part of my project (if it makes it in at all), and I didn't feel comfortable with wiring up a speaker directly to my board, I was just looking for a simple circuit I could put together from radio shack parts. If I order any parts online it'll most likely cost me several dollars in shipping and I just can't justify that for a pennies worth of parts. On the other hand, I don't want to have any additional components than necessary so I'm caught between cost, effort and number of parts. A couple of resistors, caps and a transistor seemed minimal.

I may just wait and use a minimalistic amp chip

http://rcarduino.blogspot.com/2012/08/adding-audio-to-arduino-projects.html

if I can identify enough parts for a Digikey or Mouser order.

Thanks