Common Emitter Audio Amplifier Question

[kzriwoga]

I'm tring to build an audio amplifier. I decided to use a basic common emitter amplifier circuit as a starting point and added a speaker to it.

**broken link removed**

I have some questions about the circuit.

1-) Is 2n2222 ok for this circuit?

Results of DC analysis: Vce = 10.06V and Ic = 1.26mA (I guess, these values will be used for choosing the transistor.)

2-) What's the output voltage of a standart mp3 player? Can it be 300mVp as I read somewhere?

3-) When I assume ß = 150 and input = 300mVp , the output is -2,13Vp . I guess it gives 1w power to speaker. Is there something wrong?

4-) Is connecting speaker parellel to output R ok?

Thank you..

 

[Nigel Goodwin]

Sorry, but you can't add a speaker to it, it's only a preamp - you need a power amp to feed a speaker.

The output 'power' of the preamp is near to zero, and it can only feed a high impedance load.

 

[kzriwoga]

Sorry, but you can't add a speaker to it, it's only a preamp - you need a power amp to feed a speaker.

The output 'power' of the preamp is near to zero, and it can only feed a high impedance load.

Can I easily change it to a real amp?

 

[Nigel Goodwin]

Can I easily change it to a real amp?

No, you need a minimum of probably four transistors to make a small power amp (although you can make a very poor one with just three).

 

[kzriwoga]

What about these ones? : **broken link removed**

 

[Nigel Goodwin]

What about these ones? : **broken link removed**

The only one with a speaker uses a transformer to match it, such designs are very poor, low power, high power consumption, and low quality. They also need more transistors in front, as the gain is very low as they use a power transistor to be able to survive the heat wasted.