Usually, the audio output from a laptop’s built-in speakers is low. A power amplifier is required to get a high volume. Here is a simple circuit to amplify the laptop’s audio output.
The circuit is built around power amplifier IC LA 4440 (IC1) and a few other components. LA4440 is a dual channel audio power amplifier. It has low distortion over a wide range of low to high frequencies with good channel separation. Inbuilt dual channels enable it for stereo and bridge amplifier applications.
In dual mode LA4440 gives 6 watts per channel and in bridge mode 19- watt output. It has ripple rejection of 46 dB. The audio effect can be realised by using two 6-watt speakers. Connect pins 2, 6 and ground of IC1 to the stereo jack which is to be used with the laptop.
Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. The circuit works off regulated 12V power supply. It is recommended to use audio input socket in the circuit board. Use a proper heat-sink for LA4440.
I have some queries-
1. What should be the Ampere of the transformer used to power this amplifier ?
2. Why there is no input coupling capacitors at pins 2 & 6 ?
3. What’s the function of bootstrap pins in an amplifier ?
Please post PCB layout for this circuit