Small Signal BJT Amplifier

A LM386 will most likely do what you want and with alot higher audio quality than any of those <SNIP> two transistor class a gain stages.
 
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Audioguru

Joined Dec 20, 2007
11,248
Students in school or in university are supposed to have teachers, instructors or professors.
Why don't students have them anymore??
 

Georacer

Joined Nov 25, 2009
5,182
Maybe because students are more numerous than ever and teachers are busier than ever trying to cope with the sheer number of students?

Please don't judge people on yesterday's standards.
 

Audioguru

Joined Dec 20, 2007
11,248
Maybe because students are more numerous than ever and teachers are busier than ever trying to cope with the sheer number of students?

Please don't judge people on yesterday's standards.
The economy of your country is judged by the rest of the world and is very different from my country.
Teachers, instructors and professors in my country do their jobs very well.
 

Georacer

Joined Nov 25, 2009
5,182
I 'll take your word for it.

But what about the OP's country? Is his country economy possibly affecting his educational system? Is he to blame for that?
 

tirnasjimmy

Joined Jul 28, 2011
2
You appear to be designing for max. power transfer by making the I/P resistance of your amp. = the O/P resistance of the source. This is sometimes the correst approach, but if used here will just loose 1/2 of your 300mV drive which will be dropped across the equivalent O/P resistance of the source. Better to keep the input resistence of your amp. at least 10x 100 ohms. In this case you could make it
100x.

As pointed out, you only need a low gain. 8x in possible off a 12V supply but probably too much. No need to bypass emitter resistor of 1st stage. Use 2nd stage as an emitter follower for pure current gain. A/C couple into the speaker.

You must do DC analysis before AC analysis to get quiescent currents correct. Lots of good notes on single bipolar transistor design on the web via Google etc. You must understand why you are doing each step of the design or you will have learned nothing.
 

Audioguru

Joined Dec 20, 2007
11,248
The class-A amplifier in post #17 needs high current transistors and a 16 ohm speaker.
I simulated it and found its voltage gain to be only 4.5 and it has horrible distortion. With an 8 ohm speaker its voltage gain is only 3 and its distortion is more.
 

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