Circuit Project Electronic

This project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. (View Circuit)
The Power Amplifier section 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 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.

Power Amplifier Parts:

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)

Related Links
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Power Amplifier OCL 50W by 741+2N3055+MJ2955
Power Amp OCL 100W by Transister MJ15003,MJ15004(with PCB)
Amp OTL 100W by 2N3055 (with PCB)

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