25W Power Amplifier with MOSFET IRF530/IRF9530


This is a MOSFET powered amplifier circuit. The circuit output will be 25 Watt RMS @ 8 Ohm (1KHz sine wave) with frequency response of 30Hz to 20KHz -1dB.

25W Power Amplifier with MOSFET IRF530/IRF9530 circuit diagram

Components Part:
R1, R4 = 47K
R2 = 4K7
R3 = 1K5
R5 = 390R
R6 = 470R
R7 = 33K
R8 = 150K
R9 = 15K
R10 = 27R
R11 = 500R
R12, R13, R16 = 10R
R14, R15 = 220R
R17 = 8R2 - 2W Resistor
R18 = R22 - 4W Resistor (wirewound)
C1 = 470nF/63V
C2 = 330pF/63V
C3, C5 = 470µF/63V
C4, C6, C8, C11 = 100nF/63V
C7 = 100µF/25V
C9 = 10pF/63V
C10 = 1µF/63V
Q1-Q5 = BC560C
Q6 = BD140
Q7 = BD139
Q8 = IRF530
Q9 = IRF9530

Circuit Notes:
  • This circuit dual polarity power supply to supply the amplifier.
  • This audio amplifier can be directly connected to CD players, tuners and tape recorders. Just add a 10K Log potentiometer (dual gang for stereo) along with a switch to cope using the different sources you need.
  • Q6 and Q7 must have a small U-shaped heatsink.
  • Q8 and Q9 must be mounted on heatsink.
  • Adjust R11 to set quiescent current at 100mA (best measured with an multimeter connected in series to Q8 Drain) with no input signal.
  • A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 to output ground. Then connect separately the input and output grounds to power supply ground.