This 4 Watt audio amplifier circuit is using TIP41 as a final stage amplifier. This amplifier circuit can provide power 4 watts at 4 ohm speaker. Transistor TIP 41 is combined with the BC547 and BC557 arranged in Darlington. The excess Darlington combination will provide current gain is much greater.
This audio amplifier circuit includes a low-power amplifiers, suitable for use CD player, MP3 player, audio computer / notebook, etc. All components are shown here easily found in the market at low prices.
You can assemble this audio amplifier circuit on a piece of PCB freely, but as it appears in the image, is an example of recommended PCB layout 60mm x 75mm. This amplifier works at a voltage of 13.8 VDC.
Actually TIP41 transistor does not require heating to reduce heat while it is operating. However, to prevent damage, if you have a piece of aluminum plate, attach little on TIP41 transistor. This will make a more stable amplifier performance.
Rf is the feedback resistor that serves to adjust the gain. In this audio amplifier circuit, the value of the resistor Rf is 4K7 to produce 4 Watts power.