This mini amplifier was tested in two stages, one with 24V, with a non-symmetrical power supply, and in 30V also with non-symmetrical power, the result you can watch in the original video at the end of this post.

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The Amplifier Circuit

The amplifier circuit is very simple to be arranged in figure 2 just below, it is divided into two stages: 

• The first stage is the pre-amplification and at the same time used as a drive to boost the output stage. It is formed by a transistor medium power the BD139, which supports a voltage of up to 80V and a current of 1.5A with 12.5 W of power, according to the Datasheet of the same.
  
  
• The second is the power stage, which is formed by the complementary transistors NPN - 2SC5200 and the PNP - 2SA1943 transistor, with 100W of power and high fidelity, whose collector current supported is 15 Amps.

Fig. 2 - Simple 3 transistors Power Amplifier schematic diagram

Note

Place the power transistors in a heat sink, especially if you are going to apply a voltage greater than 20V and use the amplifier continuously, they will heat up.

Component List

• T1 ---------- NPN 2SC5200 Power complementary transistor
• T2 ---------- PNP Complementary Power Transistor 2SA1943
• T3 ---------- NPN BD139 transistor
  
  
• D1, D2 ----- Diode 1N4007
  
  
• C1 ---------- Electrolytic capacitor 2.200uF - 63V
• C2 ---------- Electrolytic capacitor 4.7uF - 25V
  
  
• R1, R2 ----- Resistor 0.22 ohms - 5W - (red, red, silver)
• R3 ---------- Resistor 1k ohms - (brown, black, red)
• R4 ---------- Resistor 100k ohms - (brown, black, yellow)
  
  
• P1 ---------- 10K ohm potentiometer
  
  
• Others ----- Wires, Welds and Etc.
  
  

Direct link to download

Click in the link below to download the Files: PCB Layout, PDF, GERBER
Click Here!!!