Wednesday, February 16, 2022

Powerful Mini Audio Amplifier using only 5 Transistors with PCB

Fig 1 -  Powerful Mini Audio Amplifier using only 5 Transistors with PCB

This is a simple amplifier that uses only 5 transistors, and provides good power, by our tests, we get close to 90W, and amazingly enough, it has a very good sound given its ultra simplicity.

The circuit is quite simple, and very easy to building, which makes it a great option for those who want to build an amplifier with good power and great cost, because it uses discrete components, cheap and easy to acquire.

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The Amplifier Circuit

The amplifier circuit is very simple to assemble, as shown in Figure 2 just below, this amplifier is divided into three basic stages: 

  • The first is the pre-amplification stage: It is formed by a differential pair set of NPN 2N5551 transistors, they are working as differential pair, which gives a very good stability in the signal sent to the next stage.

  • The second is the driver stage: it is formed by the PNP TIP42 transistor, it is used as a current amplifier and serves to drive the output stage.

  • The third is the power stage: It is formed by a pair of differential power transistors, one is the NPN 2SC5200 and the other is the 2SA1943, they are in push-pull mode, configured to work in class AB, with base BIAS diodes.
  • Fig. 2 - Schematic diagram Powerful Mini Audio Amplifier using only 5 Transistors

Note

Place the power transistors on a heat-sink, because since you work with power, they will get hot, a small size radiator will help.

For those who like loud sound, to really force the amplifier to the maximum, it is recommended to put the BIAS diodes in series, on the heat sink along with the transistors. This will cause the base voltage to be controlled according to the temperature of the transistors.

Power Supply

The power is supplied through a 24 VAC transformer, after rectification the supply will provide 35 VDCThe current to power this amplifier is at least 3A, for those mounting two of these to form a stereo pair, you should double the current to 6 Amps. 

Component List

  • Semiconductor
    • Q1, Q2 .......... 2N5551 NPN Transistor 
    • Q3 ................. PNP BD140 Transistor
    • Q4 ................. 2SC5200 NPN Power complementary transistor
    • Q5 ................. 2SA1943 PNP Power complementary transistor
    • D1, D2, D3 ... 1N4007 Diode

  • Resistors
    • R1, R5 .......... 100K ohms Resistor - (brown, black, yellow, gold)
    • R2 ................. 6K8 ohms Resistor - (blue, gray, red, gold)
    • R3 ................. 620 ohms Resistor - (blue, red, brown, gold)
    • R4.................. 4K7 ohms Resistor - (yellow, violet, red, gold)
    • R6 ................. 1k5 ohms Resistor - (brown, green, red, gold)
    • R7, R8 ........... 0.22 ohms - 5W  Resistor - (red, red, silver, gold)
    • P1 .................. 10K ohm potentiometer

  • Capacitors
    • C1 ................ 2.2uF Polyester / Ceramic Capacitor
    • C2 ................ 47uF - 65V Electrolytic capacitor 

  • Miscellanies
    • P1 ................. Screw Terminal Type 5mm 2-Pin Connector
    • P2 ................. Screw Terminal Type 5mm 3-Pin Connector
    • J1 .................. Set of male connectors 2-Pin (Optional)
    • Other ............. PCB, Wires, Speaker, Heat Sink, etc.

Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 3 - PCB - Powerful Mini Audio Amplifier using only 5 Transistors

Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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My Best Regards!!!

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