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50W RMS Audio Amplifier with IRF530 and IRF9530 Mosfet + PCB

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.

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.

Components 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)
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

Any questions, suggestions, corrections, please leave them in the comments below, which we will soon be answering.

My best Regards to You!!!


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