Fig. 1 - PCB 300W RMS Power Amplifier - 2SC3858 and 2SA1494 Transistors

This amplifier has an excellent audio quality, and use four output power transistors, it reaches a sound power of 300W RMS under load of 4 ohms, powered with a symmetric power supply. You can check the schematic diagram in Figure 2 below.

Fig. 2 - Schematic 300W RMS Power Amplifier - 2SC3858 and 2SA1494 Transistors

Power Supply

The power supply consists of a symmetrical transformer 45V - 0 - 45V center tape, 6 Amperes current supply, can be used. After rectified, we will have approximately 63Vcc at the output of the symmetrical power supply .

Components list

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Fig. 1 - PCB 50W Audio Amplifier

For Portuguese version, click here!

This circuit amplifier is very simple to building, however, although simple, it has an excellent audio quality, and with just two output transistors, it reaches a sound power of 50W RMS under load of 8 ohms, which is enough for a great home sound system, or for speakers for musical instruments ... the possibilities are endless.

The first stage of the amplifier is a differential amplifier based on the transistors Q1 and Q2. Capacitor C2 is the input DC decouple, R1 limits the input current and capacitor C1 deflects unwanted high frequencies.

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The second stage is the drive stage composed of the transistor Q3 BC546, which supplies the output power stage, and the transistor Q4 is the bias regulating transistor, which, through the PR1 trimpot, adjusts the quiescent current in the transistors.

The output stage is a complementary push-pull stage based on the IRF530 and IRF9530 MOSFETs. The output is coupled to the speaker using the L1 inductor. 

The network composed in series by hairs, resistor R14 and capacitor C5, is intended to reduce output noise. And Capacitors C6 and C7 are power supply voltage filters. 

For coil L1: Wrap 12 turns of enameled copper wire in a 1cm diameter without core.

A Heatsink is required for MOSFETs. That should have the average dimensions of 8x4x4 inches will already work without problems.

You can check the schematic diagram in Figure 2 below.

Fig. 2 - 50 Watt Amplifier Circuit Diagram

Power Supply

The power supply consists of a symmetrical transformer 35Vcc - 0 - 35V center tape, with a current of 3 Amperes, a lower current, up to 2 Amperes minimum, can be used, which will play without any problems. 

Nothing prevents you from using a higher or lower voltage, as this amplifier has a tolerance for the supply voltage, and can normally play "with small attenuations in the output power" with voltages ranging from 27V to 40V without too many problems.

It also has great stability and we can use, if you have, a SMPS power supply, and this is clear with Center-Tape, that is to say a power supply with central socket.

Component List

• Q1, Q2 ................ 2N3906 Transistor (or BC558, A733)
• Q3, Q4 ................ 2N3904 Transistor (or BC548)
• Q5 ....................... IRF9530P Mosfet P Transistor
• Q6 ....................... IRF530P Mosfet N Transistor
  
  
• D1 ....................... 1N4007 Diode 
  
  
• C1 ....................... 220pF ceramic / polyester capacitor  
• C2, C3, C4 .......... 47uF - 35V electrolytic capacitor 
• C5 ....................... 68nF ceramic / polyester capacitor 
• C6, C7 ................ 470uF - 50V electrolytic capacitor 
  
  
• R1, R8 ................ 4.7k ohms resistor (yellow, violet, red, gold)
• R2, R7 ................ 47k ohms resistor (yellow, violet, orange, gold)
• R3 ....................... 560 ohms resistor (green, blue, brown, gold)
• R4 ....................... 15k ohms resistor (brown, green, orange, gold)
• R5 ....................... 1.2k ohms resistor (brown, red, red, gold)
• R6 ....................... 2.2k ohms resistor (red, red, red, gold)
• R9 ....................... 10k ohms resistor (brown, black, orange, gold)
• R10 ..................... 820 ohms resistor (gray, red, brown, gold)
• R11, R12 ............ 2.7k ohms resistor (red, violet, red, gold)
• R13, R14 ............ 680 ohms resistor (blue, gray, brown, gold)
• R15 ..................... 10 ohm - 3W resistor - (brown, black, black. gold)
  
  
• L1 ........................ 5uH - Air Core Coil 10 Turns 18AWG, 3/8" Core
  
  
• RP1 ..................... 1K ohms variable resistor - Trimpot 
  
  
• Others ................. Loudspeaker, Wires, Solders and Etc.
  
  

For those who want to download materials such as the schematic diagram in PDF, PCB Layout,  GERBER and JPG, we are providing a direct link to download all the material.

Direct link to download

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

Fig. 1 - 100W RMS Power Amplifier using 2 NPN 2SC5200 Output Transistors + PCB

For Portuguese version, click here!

We usually have amplifiers with complementary outputs on most amplifier designs, and in a vast majority of amplifiers, it's quite normal to use the complementary NPN 2SC5200 transistors in conjunction with the PNP 2SA1943.

This type of amplifier is very common and good quality, because these transistors are specific for high fidelity amplification.

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We'll build an amplifier circuit that uses the same concepts as two output transistors, but we will use two NPN 2SA5200 output transistors. Which is very interesting for those who like to test other types of transistors to evaluate the quality, distortions, powers. Etc.

The schematic diagram is in Figure 2 below, it is a simple amplifier, it has a satisfactory quality.

Fig. 2 - 100W RMS Power Amplifier with 2 NSC 2SC5200 Transistors at Output

Power Supply

The power supply consists of a symmetrical transformer 32V - 0 - 32V center tape, with a current of 5 Amperes, a lower current, up to 3 Amperes minimum, can be used, which will play without any problems.

Nothing prevents you from using a higher or lower voltage, as this amplifier has a tolerance for the supply voltage, and can normally play “with small attenuation in the output power” with voltages ranging from 18V to 55V without too many difficulties.

It also has great stability, and we can use, if you have, a SMPS power supply, and this is clear with Center-Tape, that is to say a power supply with central socket.

Component List

• Q1, Q2 ............... Transistor A733
• Q3, Q4 ............... TIP41C transistor
• Q5 ...................... TIP42C transistor
• Q6, Q7 ............... 2SC5200 Power Transistor
  
  
• D1, D2, D3 ........ Diode 1N4007
  
  
• C1 ....................... 0.47uF Polyester capacitor 
• C2, C4, C5 .......... 47uF - 63V electrolytic capacitor 
• C3 ....................... 100nF ceramic / polyester capacitor 
• C6 ....................... 150pF ceramic / polyester capacitor 
• C7, C8 ................ 1nF ceramic / polyester capacitor
  
  
• R1 ....................... 22k ohms resistor (red, red, orange, gold)
• R2 ....................... 15k ohms resistor (brown, green, orange, gold)
• R3, R7 ................. 680 ohms resistor (blue, gray, brown, gold)
• R4 ....................... 33 ohms resistor (orange, orange, black, gold)
• R5 ....................... 560 ohms - 1W resistor (green, blue, brown, gold)
• R6 ....................... 56k ohms resistor (green, blue, orange, gold)
• R8, R9 ................ 4.7k ohms resistor (yellow, violet, red, gold)
• R10 ..................... 10 ohm resistor - (brown, black, black. gold)
• R11 ..................... 120 ohms - 1W resistor (brown, red, brown, gold)
• R12, R13 ............ 100 ohms - 1W resistor (brown, black, brown, gold)
• R14, R15 ............ 0.47 ohms - 5W resistor (yellow, violet, silver, gold)
  
  
• Others ................. PCB, Heat Sink, Loudspeaker, Wires, Solders, Etc.
  
  

For those who want to download materials such as the schematic diagram in PDF, PCB Layout,  GERBER and JPG, we are providing a direct link to download all the material.

Direct link to download

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