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How do I make a 50W amplifier using BJT's? We need to use 24V source. For some reason, we weren't able to make it work. without the load resistor (which is supposed to be a 4 ohm speaker), the circuit amplifies from 300mV to approximately 5V. What can I do to make it work? Or is there a good design I can follow?

Specifications: 24V, 50+W, Using BJT transistor, resistors, and capacitors. (No Op-Amp) 4 ohm speaker for the output, the frequency response can be any good range for mp3 songs. Minimized noise and distortion. enter image description here

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    \$\begingroup\$ What's your actual question here? "It doesn't work" is, as you probably understand, not helpful. Post your schematic and it may be possible to help. \$\endgroup\$ – pipe Oct 15 '16 at 12:03
  • \$\begingroup\$ I prepared a screenshot already but I forgot to attach it. I just attached it now. I apologize about that. \$\endgroup\$ – JRA Oct 15 '16 at 12:14
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    \$\begingroup\$ There are plenty of good designs to follow and searching for 50W audio transistor amplifier will find at least some of them. None of them use a single 2N2222 however. \$\endgroup\$ – Brian Drummond Oct 15 '16 at 12:23
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A 24 volt supply with a single push pull output stage can, at absolute best, deliver an undistorted sinewave of 18 watts to a 4 ohm load. If you used two such push pull stages in a bridge you can achieve 72 watts.

So, you need to be looking for a design that is based around what I've described above. This site isn't a free design service so I suggest you do some research around what I've said and come back with a circuit proposal.

The design you have shown is totally unsuitable.

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  • \$\begingroup\$ Is there anyway to fix it? \$\endgroup\$ – JRA Oct 15 '16 at 13:28
  • \$\begingroup\$ If there was an "easy fix" for that design would Andy write: The design you have shown is totally unsuitable. ? Take it from me, he would not. What you need to do is educate yourself on (audio) amplifier design. Or find a design of a proper audio amplifier and learn how that works. You start with a simple CE stage and expect it to perform a miracle because you have no clue. So get a clue and learn this properly (yes the hard way). \$\endgroup\$ – Bimpelrekkie Oct 15 '16 at 13:52
  • \$\begingroup\$ @JRA No, un-fixable Two bridge amplifiers as Andy says. Your 24v supply should be capable of supplying about four amps average. It is a big project. \$\endgroup\$ – glen_geek Oct 15 '16 at 13:57

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