This two-channel amplifier provides power to 20 watts RMS from two line inputs. Ideal for use in computers since its price / performance / complexity is optimal.
In the 20 watt stereo amplifier circuit observed only one stage of the system because the circuit stereo, second channel are identical. The figures in parentheses are equivalent to the terminal for second channel. The core of this project is the integrated circuits from National Semiconductor, the LM1876, which provides two power operational amplifier with mute and standby function.
The input signal, that having been conditioned and leveled, will enter into non-inverting amplifier input. At the output of op amp part of the resulting signal is fed back to the inverting amplifier to form a feedback network. Because the circuit is internally balanced when working with source item is not necessary to install the output BootStrap capacitor.
This system requires an operating voltage + / -28 volts and 2 amps current. In this case the transformer should have a primary according to the mains voltage (220V) and a secondary ct of each branch 20v (40v from end to end). The diodes must be 100V / 3A 1N5406 or similar type. Can also be used a bridge rectifier, which makes it easier and reduces the number of tracks / space. The filter capacitors are 4700μF x 50v.
And be sure to provide a heatsink to the IC amplifier.