How to Make Ultra-High Performance 20W Amplifier Circuit by Using TDA7377 Powered by 12V Battery

 This is an ideal project for those who want a compact stereo amplifier that can run on a 12V battery. This could be just the ticket for traveling musicians who want a small but brave amplifier powered by SLA batteries, or it can be used anywhere 12V DC is available - in cars, RVs, Insulated house with 12V DC or anywhere. Because it runs on DC power it would be an ideal project for beginners or students, no need to worry about 240V AC power.

You can run it from a 12V battery or a DC outlet block. But even if it's compact and easy to build, you don't need to apologize for "just average" performance. In listening tests on a variety of compact discs, we were impressed with the sound quality. However, by using the TDA7377 power amplifier IC and making other improvements, the THD (Total Harmonic Distortion) of this design is about 50 times better than the other ones. The bottom line is that THD under normal conditions is around 0.03% or less.

It can also provide more output power thanks to the improved output transistors of the new power amplifier IC. Moreover, its idle power consumption is low - no more than 1W. As a result, if you don't press too hard, the device will run cool and not drain the battery too quickly. And since the IC has a self-protecting circuit, it is virtually indestructible. It will self-limit or turn off if it gets too hot and the output will turn off if shorted.

Obtaining enough power

With a 12V power supply, the maximum voltage fluctuation a typical solid-state power amplifier can produce is ±6V. This yields a meager 4.5W RMS at 4O and 2.25W RMS at 8O without accounting for losses in the output transistor. While the DC power is around 14.4V (the maximum one can generally expect from a 12V car battery), this only brings the power up to 6.48W and 3.24 W to the load respectively. is 4O and 8O – still not really enough. There are three common solutions to this problem. 

The first is to increase the supply voltage using a switching DC converter. This greatly increases the cost and complexity of the amplifier, but it's a way to get a lot of power out of a 12V power supply. However, we wanted to keep this project simple and this precludes this technique. The second method is to reduce the impedance of the speaker. Some car speakers have impedances as low as 2 ohm, which can deliver twice as much power for the same supply voltage. However, we do not want to limit this amplifier to a 2 ohm speaker.