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Post subject: My Amplifier Based on 2N3055
Posted: Mon Jul 10, 2017 1:51 am
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Joined: Thu Apr 27, 2017 8:18 pm
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Good day~
Please look at the following circuit:
Image
This a 24 Watt Class A Amplifier circuit made from discrete semiconductors like 2N3055. This audio amplifier can drive up to 24W Class A into 8 Ohm speaker with an audio bandwidth of 100mHz to 100kHz flat. The input power is 305mV for 24W output into 8 Ohm (33dB gain) and the THD is very low.
The datasheet of 2N3055
The supply voltage can be between 34V and 46V and the quiescent current should be set to 1.7A measured through R25 (a voltage of 0.75V must be measured over R25 for a quiescent current of just under 1.7A). R23 is a trimmer and must be set to maximum resistance (10kOhm) when powering up.
Then the resistance of R23 must be decreased until the the quiescent current is achieved. If the amplifier is mounted on a big enough heatsink ( 0.6K/W at most) then the amplifier is very safe from thermal runaway. Intelligence must be used when choosing power and voltage ratings of resistors and capacitors.


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Post subject: Re: My Amplifier Based on 2N3055
Posted: Tue Jul 11, 2017 8:38 pm
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Professional Musician
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Joined: Thu Aug 07, 2014 3:25 pm
Posts: 1023
You may as well build a smoke bomb, cause that's what this design will do. You can't use 2n2222 to drive that much current into the 3055s. You should be using to220 drivers. The feedback loop should probably be connected to the other side of the differential input pair.
I'm assuming the other differential pair is for bias compensation. I've never seen such an approach.
It doesn't look like a stable setup.
Setting up a system like this will require gain selected transistors to achieve bias and balance. Both the differential pairs need to be gain matched as well.
The 2n2222 are too low gain for an input device and too high gain for the driver stages.
I can tell you from experience that class A solid state is a tough thing to get right and temperature stable.
Also, the reactance of the output capacitor will affect the falling wave as the transistors turn off. Consider a transformer coupled class A. But don't build this one.


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Post subject: Re: My Amplifier Based on 2N3055
Posted: Fri Jul 14, 2017 8:50 am
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Joined: Thu Aug 07, 2014 3:25 pm
Posts: 1023
Nama, I see you are the smoke bomb.
I google class a schematics and "yours" is the first result. Credited to someone else.
You are the first to make my sh%& list.


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