Stereo amplifiers refers to the type of amplifiers that has two output and input channels.The weak input signal fed into two channels will be amplified and power will be boosted in the output channels.This circuit is capable of delivering 6 watts power to speakers.
LA4440
This circuit uses stereo chipIC LA4440with built in stereo input and output channels.LA4440 is capable of operating from 12V to 18V.Adding to that this chip can deliver a power of 6W to each output channels while operating at stereo mode.This amplifier can deliver a gain of about 53.5dB to the incoming signal.
Working of Stereo Power Amplifier
The IN1 and IN2 pins are two input stereo channels through which the weak audio signal will be fed.Capacitor C10 and C1 removes DC elements in the signal.Resistor R3 and R4 will act as a volume control.The pin 2 and 6 connects to internal audio amplifier stage of the chip LA4440 IC.The amplified output from this stage is fed to driver amplifier and then followed by output stage.The amplified signal will be obtained from output pin 12 and 10.
The capacitor C1 is a feedback capacitor, this decides the lower cutoff frequency of the amplifier.Lowering the capacitor value will increase the cutoff frequency of the input signal.
The Capacitor C9 used with pin 5 acts as a ripple filter.The C3 capacitor connected from Pin 13 acts as a bootstrap capacitor.This will provide bias voltage for output stage and thus allows output signal to reach rail to rail voltage.
The coupling capacitor from output pin 12 and 10 is used to filter out any DC noise elements in the signal.It is followed by a RC ( C5R1 & C6R2 ) network that prevents oscillations in the output signal.This will enable LA4440 to deliver a stable signal in the output.
LM380,NE612