Hi, we were asked to make an audio amplifier using only bjt in net and build it could someone help me. I found a circuit but when I simulate it using proteus it doesnt have perfect wave as it supposedly. Heres the circuit diagram

 

hi ganny,
Do you have an image of the output waveform that you could post.?
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Thanks for response. Here is the output waveform together with the input waveform (50mV, 1kHz) By the it the output waveform also change depending on the frequency

 

hi,
Is the waveform at say, 10mV OK.
That image appears that you are over driving it.
If you have a link to that web page I will have a look.
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Here is it
http://www.circuitstoday.com/few-transistor-amplifier-circuits#class-ab

 

hi,
Read thru your link, will try it out using LTSpice, give me a little while, I will post back later.
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1mv pk to pk works fine... The output is 1v pk to pk.. anything much over 2mV is clipped..

 

1mv pk to pk works fine... The output is 1v pk to pk.. anything much over 2mV is clipped..

Thanks for your response. Is there a good thing about it? Especially when the input signal is not that kind of amplitude correct me if I am wrong thanks

hi,
Read thru your link, will try it out using LTSpice, give me a little while, I will post back later.
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Effort Appreciated. I'll wait for you

 

hi ganny,
Here you go, add a 220R in the emitter of the first transistor stage,
Works OK upto 20mV .
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Lets wait for Eric... If his results are the same as mine....


Yep!! But it seems now the fist stage is attenuating 20mV to 10mV.. Works better though..

 

But I didnt get the same output look. For 10 mV. Im not satisfied by this circuit. Do you have guys any suggestions? A legit audio amp circuit?

 

hi,
Are you using the exact components as shown in the original drawing.???

It works perfectly well upto 30mV, with minimum cross over distortion.

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@ganny Change your 2n2222's to 2n2222a's and change all your caps to the cap-elec models..

Here's a screenshot of the three waveforms I get on Proteus.. Vey similar to Erics..

 

Yes, I used the same components. I checked it many times

Is there difference between 2n2222 and 2n222a? Thanks

 

Yes, I used the same components. I checked it many times

Hi g,
There must be something different or maybe a faulty component.?

Can you post a clear photo of the project.?
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Yeah!! I found the model 2n2222 is rubbish... The a's work okay!!

 

Here the unchanged

 

hi g,
Are you saying you have not actually built this circuit.?
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Here the unchanged

hi g,
Are you saying you have not actually built this circuit.?
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I built it. But I need somthing works well

Could you find me alternative circuit on net that works well?

 

Hello,

ESP has a lot of projects, you could have a look at:
http://sound.whsites.net/projects-0.htm

Bertus