Our Arduino project on doorbell is a great, simple project but if you followed that guide, you have probably noticed the volume of the sound that we are generating using a buzzer or speaker connected to an Arduino is not enough loud to be useful as a doorbell.
That’s why we need to slightly modify such projects and amplify the sound. TDA7297 amplifier module can be powered by 6-18V and is capable to produce a loud, stereo sound. We can also just use one speaker with this module. The price tag of this module, as can be expected is not too high (around $5).
An alternative solution PAM8403 chip-based amplifier modules, is more easily available. Although it is a low-power solution it does not produce the good sound amplification required for doorbell projects.
TDA7297 Audio Amplifier Module is not a linear amplifier. It converts our input to PWM, amplifies that, and then smooths it with capacitors. It is only suitable for projects with a limited frequency range, which should be perfectly fine for our intended audio application.
It is a class D audio power amplifier with TDA7297 core technology for the BTL bridge circuit. A Class D amplifier is an audio amplifier that is primarily used as a power amplifier. It is characteristic that an analogue or digital audio signal is brought into a sequence of pulses. This allows the power amplifier to operate in switching mode, which means that its transistors are either maximally conductive or maximally insulating and thus only know two states. These two working ranges have little power dissipation, in contrast to the intermediate states of linear operation used in conventional Class A, B or AB amplifiers. These characters are suitable for our project.
TDA7297 was originally manufactured by STMicroelectronics. On the datasheet, it is written: “The TDA7297 is a dual bridge amplifier specially designed for TV and Portable Radio applications.” Probably they are talking about old electronics.