Wiring Schematic Diagram

Mosfet Audio Power Amplifier 18W

This audio project is designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality.



This audio amplifier circuit employs only three transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm with <0.08% THD @ 1KHz at the onset of clipping (0.04% @ 1W - 1KHz and 0.02% @ 1W - 10KHz) and up to 30W into a 4 Ohm load.




To obtain such a performance and to ensure overall stability of this very simple circuitry, a suitable regulated dc power supply is mandatory. This is not a snag because it also helps in keeping noise and hum of the preamp to very low levels and guarantees a predictable output power into different load impedances. Finally, as the audio amplifier requires only a single rail supply, a very good dc voltage regulator capable of supplying more than 2 Amps @ 40V can be implemented with a few parts also.


Audio power amplifier Parts List:

R1=2K2 1/4W Resistor
R2=27K 1/4W Resistor
R3,R4=2K2 1/2W Trimmers Cermet or Carbon (or 2K)
R5=100R 1/4W Resistor
R6=1K 1/4W Resistor R7,
R8=330R 1/4W Resistors

C1=22µF 25V Electrolytic Capacitor
C2=47pF 63V Polystyrene or Ceramic Capacitor
C3,C4=100µF 50V Electrolytic Capacitors
C5=2200µF 50V Electrolytic Capacitor

Q1=BC550C 45V 100mA Low noise High gain NPN Transistor
Q2=IRF530 100V 14A N-Channel Hexfet Transistor (or MTP12N10)
Q3=IRF9530 100V 12A P-Channel Hexfet Transistor (or MTP12P10)